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Subject: sed FAQ, version 014

This article was archived around: Fri, 28 Apr 2000 15:14:15 GMT

All FAQs in Directory: editor-faq
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Archive-name: editor-faq/sed Posting-Frequency: bimonthly Last-modified: 2000/04/28 Version: 014 URL: http://www.cornerstonemag.com/sed/sedfaq.html Maintainer: Eric Pement <epement@jpusa.chi.il.us>
THE SED FAQ Frequently Asked Questions about sed, the stream editor CONTENTS: 1. GENERAL INFORMATION 1.1. Introduction - How this FAQ is organized 1.2. Latest version of the sed FAQ 1.3. FAQ revision information 1.4. How do I add a question/answer to the sed FAQ? 1.5. FAQ abbreviations 1.6. Credits and acknowledgements 1.7. Standard disclaimers 2. BASIC SED 2.1. What is sed? 2.2. What versions of sed are there, and where can I get them? 2.2.1. Free versions 2.2.1.1. Unix platforms 2.2.1.2. OS/2 2.2.1.3. Microsoft Windows (Win3x, Win9x, WinNT, Win2K) 2.2.1.4. MS-DOS 2.2.1.5. CP/M 2.2.2. Shareware and Commercial versions 2.2.2.1. Unix platforms 2.2.2.2. OS/2 2.2.2.3. Windows 95/98, Windows NT, Windows 2000 2.2.2.4. MS-DOS 2.3. Where can I learn to use sed? 2.3.1. Books 2.3.2. Mailing list 2.3.3. Tutorials, electronic text 2.3.4. General web and ftp sites 3. TECHNICAL 3.1. More detailed explanation of basic sed 3.2. Common one-line sed scripts. How do I . . . ? - double/triple-space a file? - convert DOS/Unix newlines? - delete leading/trailing spaces? - do substitutions on all/certain lines? - delete consecutive blank lines? - delete blank lines at the top/end of the file? 3.3. Addressing and address ranges 3.4. [reserved] 3.5. [reserved] 3.6. Notes about s2p, the sed-to-perl translator 3.7. GNU/POSIX extensions to regular expressions 4. EXAMPLES 4.1. How do I perform a case-insensitive search? 4.2. How do I make changes in only part of a file? 4.3. How do I change only the first occurrence of a pattern? 4.4. How do I make substitutions in every file in a directory, or in a complete directory tree? 4.4.1 - Perl solution 4.4.2 - Unix solution 4.4.3 - DOS solution 4.5. How do I parse a comma-delimited data file? 4.6. How do I insert a newline into the RHS of a substitution? 4.7. How do I represent control-codes or non-printable characters? 4.8. How do I read environment variables with sed? 4.8.1. - on Unix platforms 4.8.2. - on MS-DOS or 4DOS platforms 4.9. How do I export or pass variables back into the environment? 4.9.1. - on Unix platforms 4.9.2. - on MS-DOS or 4DOS platforms 4.10. How do I handle shell quoting in sed? 4.11. How do I delete a block of text if the block contains a certain regular expression? 4.12. How do I locate/print a paragraph of text if the paragraph contains a certain regular expression? 4.13. How do I delete a block of _specific_ consecutive lines? 4.14. How do I read (insert/add) a file at the top of a textfile? 4.15. How do I address all the lines between RE1 and RE2, excluding the lines themselves? 4.16. How do I replace "/some/UNIX/path" in a substitution? 4.17. How do I replace "C:\SOME\DOS\PATH" in a substitution? 4.18. How do I convert files with toggle characters, like +this+, to look like [i]this[/i]? 4.19. How do I delete only the first occurrence of a pattern? 4.20. How do I commify a string of numbers? 5. WHY ISN'T THIS WORKING? 5.1. Why don't my variables like $var get expanded in my sed script? 5.2. I'm using 'p' to print, but I have duplicate lines sometimes. 5.3. Why does my DOS version of sed process a file part-way through and then quit? 5.4. My RE isn't matching/deleting what I want it to. (Or, "Greedy vs. stingy pattern matching") 5.5. What is CSDPMI*B.ZIP and why do I need it? 5.6. Where are the man pages for GNU sed? 5.7. How do I tell what version of sed I am using? 5.8. Does sed issue an exit code? 5.9. The 'r' command isn't inserting the file into the text. 5.10. Why can't I match or delete a newline using the \n escape | sequence? Why can't I match 2 or more lines using \n? | 5.11. My script aborts with an error message, "event not found". | 6. OTHER ISSUES 6.1. I have a problem that stumps me. Where can I get help? 6.2. How does sed compare with awk, perl, and other utilities? 6.3. When should I use sed? 6.4. When should I NOT use sed? 6.5. When should I ignore sed and use Awk or Perl instead? 6.6. Known limitations among sed versions 6.7. Known bugs among sed versions 6.8. Known incompatibilities between sed versions 6.8.1. Issuing commands from the command line 6.8.2. Using comments (prefixed by the '#' sign) 6.8.3. Special syntax in REs 6.8.4. Word boundaries 6.8.5. Range addressing with GNU sed and HHsed 6.8.6. Commands which operate differently | ------------------------------ 1. GENERAL INFORMATION 1.1. Introduction - How this FAQ is organized This FAQ is organized to answer common (and some uncommon) questions about sed, quickly. If you see a term or abbreviation in the examples that seems unclear, see if the term is defined in section 1.5. If not, write us and we'll try to clarify it for the next version of the FAQ. 1.2. Latest version of the sed FAQ The newest version of the sed FAQ is usually here: http://www.cornerstonemag.com/sed/sedfaq.html http://www.cornerstonemag.com/sed/sedfaq.txt http://www.dbnet.ece.ntua.gr/~george/sed/sedfaq.html http://www.dbnet.ece.ntua.gr/~george/sed/sedfaq.txt http://www.ptug.org/sed/sedfaq.html http://www.faqs.org/faqs/editor-faq/sed ftp://rtfm.mit.edu/pub/faqs/editor-faq/sed Another FAQ file on sed by a different author can be found here: http://www.dreamwvr.com/sed-info/sed-faq.html 1.3. FAQ revision information Changes to this FAQ since the last version are indicated by a vertical bar (|) placed in column 78 of the affected lines. To remove the vertical bars (use double quotes for MS-DOS): sed 's/ *|$//' sedfaq.txt > sedfaq2.txt In the HTML version, vertical bars do not appear. New or altered portions of the FAQ are indicated by printing in dark blue type. In the text version, words needing emphasis may be surrounded by the underscore '_' or the asterisk '*'. In the HTML version, these are changed to italics and boldface, respectively. 1.4. How do I add a question/answer to the sed FAQ? Word your question succinctly and clearly, and e-mail it Eric Pement <epement@jpusa.org>, indicating your proposed addition to the FAQ. We'll post it on the sed-users mailing list (see section 2.3.2, below) and discuss it there. If some agreement, your contribution will be included in the next edition of the FAQ. 1.5. FAQ abbreviations: files = one or more filenames, separated by whitespace RE = Regular Expressions supported by sed LHS = the left-hand side ("find" part) of "s/find/repl/" command RHS = the right-hand side ("replace" part) of "s/find/repl/" cmd. files: "files" stands for one or more filenames entered on the command line. The names may include any wildcards your shell understands (such as ``zork*'' or ``Aug[4-9].let''). Sed will process each filename passed to it by the shell. RE: For the syntax of Basic Regular Expressions (BREs), type "man ed" and read the documentation for regular expressions. A technical description of BREs from the Single UNIX Specification, Version 2, by The Open Group (joint committee on Unix) is available online at <http://www.opengroup.org/onlinepubs/7908799/xbd/re.html#tag_007_003>. | Sed normally supports BREs plus '\n' to match a newline in the pattern space and '\xREx' as equivalent to '/RE/', where 'x' is any character other than another backslash. Some versions of sed support supersets of BREs, or "extended regular expressions", which offer additional metacharacters for increased flexibility. For additional information on extended REs in GNU sed, see sections 3.7 ("GNU/POSIX extensions to regular expressions") and 6.8.3 ("Special syntax in REs"), below. LHS: In sed, the LHS may be a string literal (e.g., "foo") or any valid regular expression supported by your version of sed. Some versions of sed support things like \t for TAB, \r for carriage return, \xNN for direct entry of hex codes, etc. Other versions of sed do not support this syntax. RHS: The right-hand side (the replacement part in s/find/replace/) is almost always a string literal, with no interpolation of the metacharacters (.), (^), ($), ([), or \(...\) -- with the following exceptions: \1 through \9 are replaced by the corresponding group, if grouping \(...\) was used in the LHS. If no grouping was used in the LHS, then \1 through \9 are replaced by literal digits. '&' is replaced by the entire expression matched on the LHS. To enter a literal ampersand or backslash in the RHS, type '\&' or '\\'. 1.6. Credits and acknowledgements My time spent messing with sed, composing this FAQ, and generally doing text manipulation which is unrelated to my job description is due to the kind tolerance of the Christian magazine I work for, Cornerstone. So, let me say thanks to the mag staff for indulging this somewhat unusual "ministry." Please visit this site: http://www.cornerstonemag.com Many of the ideas for this FAQ were taken from the Awk FAQ http://www.faqs.org/faqs/computer-lang/awk/faq/ ftp://rtfm.mit.edu/pub/usenet/comp.lang.awk/faq and from the Perl FAQ http://www.perl.com/perl/FAQ http://www.perl.com/CPAN/doc/FAQs/FAQ/html/index.html ftp://ftp.cdrom.com/pub/perl/CPAN/doc/FAQs/FAQ The following individuals have contributed significantly to this document, and have provided input and wording suggestions for questions, answers, and script examples. Credit goes to these contributors (in alphabetical order by last name): Al Aab <af137@freenet*toronto*on*ca> Yiorgos Adamopoulos <adamo@softlab*ece*ntua*gr> Walter Briscoe <walter@wbriscoe*demon*co*uk> Jim Dennis <jadestar@rahul*net> Carlos Duarte <cdua@algos*inesc*pt> Otavio Exel <oexel@economatica*com*br> Mark Katz <mark@ispc001*demon*co*uk> Eric Pement <epement@jpusa*org> | Greg Pfeiffer <gpfeiffe@yahoo*com> Ken Pizzini <ken@halcyon*com> Niall Smart <nialls@euristix*ie> Simon Taylor <staylor@unisolve*com*au> Greg Ubben <gsu@romulus*ncsc*mil> Note: Periods (.) are replaced with asterisks (*) to foil e-mail harvesting and spam-bots. 1.7. Standard disclaimers While a serious attempt has been made to ensure the accuracy of the information presented herein, the contributors and maintainers of this document do not claim the absence of errors and make no warranties on the information provided. If you notice any errors or ambiguous wording, please notify the FAQ maintainer so it can be fixed for the next edition. ------------------------------ 2. BASIC SED 2.1. What is sed? "sed" stands for Stream EDitor. Sed is a non-interactive editor, written by the late Lee E. McMahon in 1973 or 1974. A brief history of sed's origins may be found in an early history of the Unix tools, at <http://www.columbia.edu/~rh120/ch106.x09>. Instead of the user altering a file interactively by moving the cursor on the screen (like with Word Perfect), the user sends a script of editing instructions to sed, plus the name of the file to edit (or the text to be edited may come as output from a pipe). In this sense, sed works like a filter -- deleting, inserting and changing characters, words, and lines of text. Its range of activity goes from small, simple changes to very complex ones. Sed reads its input from stdin (Unix shorthand for "standard input," i.e., the console) or from files (or both), and sends the results to stdout ("standard output," normally the console or screen). Most people use sed first for its substitution features. Sed is often used as a find-and-replace tool. sed 's/Glenn/Harold/g' oldfile >newfile will replace every occurrence of "Glenn" with the word "Harold", wherever it occurs in the file. The "find" portion is a regular expression ("RE"), which can be a simple word or may contain special characters to allow greater flexibility (for example, to prevent "Glenn" from also matching "Glennon"). My very first use of sed was to add 8 spaces to the left side of a file, so when I printed it, the printing wouldn't begin at the absolute left edge of a piece of paper. sed 's/^/ /' myfile >newfile # my first sed script sed 's/^/ /' myfile | lp # my next sed script Then I learned that sed could display only one paragraph of a file, beginning at the phrase "and where it came" and ending at the phrase "for all people". My script looked like this: sed -n '/and where it came/,/for all people/p' myfile Sed's normal behavior is to print (i.e., display or show on screen) the entire file, including the parts that haven't been altered, unless you use the -n switch. The "-n" stands for "no output". This switch is almost always used in conjunction with a 'p' command somewhere, which says to print only the sections of the file that have been specified. The -n switch with the 'p' command allow for parts of a file to be printed (i.e., sent to the console). Next, I found that sed could show me only (say) lines 12-18 of a file and not show me the rest. This was very handy when I needed to review only part of a long file and I didn't want to alter it. sed -n 12,18p myfile # the 'p' stands for print Likewise, sed could show me everything else BUT those particular lines, without physically changing the file on the disk: sed 12,18d myfile # the 'd' stands for delete Sed could also double-space my single-spaced file when it came time to print it: sed G myfile >newfile If you have many editing commands (for deleting, adding, substituting, etc.) which might take up several lines, those commands can be put into a separate file and all of the commands in the file applied to file being edited: sed -f script.sed myfile # 'script.sed' is the file of commands # 'myfile' is the file being changed It is not our intention to convert this FAQ file into a full-blown sed tutorial (for good tutorials, see section 2.3). Rather, we hope this gives the complete novice a few ideas of how sed can be used. 2.2. What versions of sed are there, and where can I get them? 2.2.1. Free versions Note: "Free" does not mean "public domain" nor does it necessarily mean you will never be charged for it. All versions of sed in this section except the CP/M versions are based on the GNU general public license and are "free software" by that standard (for details, see http://www.gnu.org/philosophy/free-sw.html). This means you can get the source code and develop it further. At the URLs listed in this category, sed binaries or source code can be downloaded and used without fees or license payments. 2.2.1.1. Unix platforms GNU sed v3.02.80 Now a,i,c commands can accept a string after them. Range syntax now supports "/RE/,+n" (next n lines) or "/RE/,~n" (till the next line which is a multiple of n). NULs permitted in regexes; \n, \t, \a, \f, \xHH hex codes supported on LHS and RHS; more changes. An alpha test release which (if found bug-free) will become GNU sed version 3.03. Supersedes GNU sed-3.02a. ftp://alpha.gnu.org/pub/gnu/sed/sed-3.02.80.tar.gz GNU sed v3.02a Interim version with most of what is now gsed-3.02.80 (above), which supersedes it. GNU sed v3.02 This is the latest official version of GNU sed ftp://ftp.gnu.org/pub/gnu/sed/sed-3.02.tar.gz GNU sed v2.05 This version is superseded by v3.02 and v3.02.80, above. GNU mirror sites. A list of mirror sites is at: http://www.ensta.fr/internet/unix/GNU-archives.html Precompiled versions: GNU sed v3.02-4 source code and binaries for Debian GNU/Linux http://www.debian.org/Packages/unstable/base/sed.html GNU sed v3.02-1 source code and binaries for Debian GNU/Linux http://www.debian.org/Packages/stable/base/sed.html The 4.4BSD version of sed is available from any 4.4BSD-Lite2 mirror site: ftp://ftp.ntua.gr/pub/bsd/4.4BSD/usr/src/usr.bin/sed/ For some time, the GNU project <http://www.gnu.org> used Eric S. Raymond's version of sed (ESR sed v1.1), but eventually dropped it because it had too many built-in limits. In 1991 Howard Helman modified the GNU/ESR sed and produced a flexible version of sed v1.5 available at several sites (Helman's version permitted things like \<...\> to delimit word boundaries, \xHH to enter hex code and \n to indicate newlines in the replace string). This version did not catch on with the GNU project and their version of sed has moved in a similar but different direction. sed v1.3, by Eric Steven Raymond (released 4 June 1998) http://earthspace.net/~esr/sed-1.3.tar.gz Eric Raymond <esr@snark.thyrsus.com> wrote one of the earliest versions of sed. On his website <http://www.tuxedo.org/~esr/> which also distributes many freeware utilities he has written or worked on, he describes sed v1.1 this way: "This is the fast, small sed originally distributed in the GNU toolkit and still distributed with Minix. The GNU people ditched it when they built their own sed around an enhanced regex package -- but it's still better for some uses (in particular, faster and less memory-intensive)." (Version 1.3 fixes an unidentified bug and adds the L command to hexdump the current pattern space.) 2.2.1.2. OS/2 GNU sed v3.02.80 | http://www2s.biglobe.ne.jp/~vtgf3mpr/gnu/sed.htm | GNU sed v2.05 (requires 'emxrt.zip', below) http://oak.oakland.edu/pub/os2/editors/gnused.zip http://oak.oakland.edu/pub/os2/emx09c/emxrt.zip GNU sed v1.06 http://oak.oakland.edu/pub/os2/editors/sed106.zip 2.2.1.3. Microsoft Windows (Win3x, Win9x, WinNT, Win2K) GNU sed v3.02.80 32-bit binaries and docs, using DJGPP compiler. For details on new features, see Unix section, above. http://www.cornerstonemag.com/sed/sed3028a.zip # DOS binaries ftp://alpha.gnu.org/pub/gnu/sed/sed-3.02.80.tar.gz # source GNU sed v3.02 32-bit binaries and source, using DJGPP compiler. Requires 80386 SX or better. Also requires 3 CWS*.EXE extenders if run under MS-DOS. See section 5.5 ("What is CSDPMI*B.ZIP and why do I need it?"), below. This version will run under Windows or under MS-DOS. The binary archive (sed302b.zip) contains 2 executables, sed.exe and gsed.exe. sed.exe was compiled with the DJGPP regex library, which is POSIX.2-compliant and usually runs faster; gsed.exe was compiled with the GNU regex library, which though it runs slower and is almost POSIX.2-compliant, it has a richer set of regexs and will run faster on certain complex regexs which cause the DJGPP sed.exe to run extremely slowly. ftp://ftp.simtel.net/pub/simtelnet/gnu/djgpp/v2gnu/sed302b.zip ftp://ftp.cdrom.com/.27/simtelnet/gnu/djgpp/v2gnu/sed302b.zip ftp://ftp.simtel.net/pub/simtelnet/gnu/djgpp/v2gnu/sed302s.zip ftp://ftp.cdrom.com/.27/simtelnet/gnu/djgpp/v2gnu/sed302s.zip GNU sed v2.05 32-bit binaries, no docs. Requires 80386 DX (SX will not run) and must be run in a DOS window or in a full screen DOS session under Microsoft Windows. Will not run in MS-DOS mode (outside Win/Win95). We recommend using GNU sed v3.02 (above) instead. http://www.simtel.net/pub/simtelnet/win95/prog/gsed205b.zip ftp://ftp.cdrom.com/.27/simtelnet/win95/prog/gsed205b.zip GNU sed v1.03 modified by Frank Whaley. ftp://ftp.itribe.net/pub/virtunix/gnused.zip Again, we recommend avoiding versions of GNU sed other than version 3.02 or 3.02.80. However, this version appears to be built on gsed v1.03 beta as a base and then augmented farther. The authors did not give this sed its own version number or name. Gsed v1.03 is offered in the "Virtually UN*X" set of Win32 utilities at <http://www.itribe.net/virtunix/>. It supports Win 95/98/NT long filenames, and runs in a DOS session or DOS window under Microsoft Windows, but does not run in DOS mode. This version of sed supports hex, decimal, binary, and octal representation in expressions. The Cygwin toolkit: http://sourceware.cygnus.com/cygwin/ Formerly know as "GNU-Win32 tools." According to their home page, "The Cygwin tools are Win32 ports of the popular GNU development tools for Windows NT, 95 and 98. They function through the use of the Cygwin library which provides a UNIX-like API on top of the Win32 API." The version of sed used is GNU sed v3.02. Minimalist GNU-Win32 (Mingw32): ftp://agnes.dida.physik.uni-essen.de/home/janjaap/mingw32/binaries/sed-2.05.zip http://agnes.dida.physik.uni-essen.de/~janjaap/mingw32/download.html According to their home page, "The Minimalist GNU-Win32 Package (or Mingw32) is simply a set of header files and initialization code which allows a GNU compiler to link programs with one of the C run-time libraries provided by Microsoft. By default it uses CRTDLL, which is built into all Win32 operating systems." The download page says Mingw32 programs "behave like you would expect from a Windows application. They support drive letters, for example. A side effect of using CRTDLL is that Mingw32 is thread-safe, while Cygwin32 is not." The version of sed used is GNU sed v2.05. sed v1.5 (a/k/a HHsed), by Howard Helman Compiled with Mingw32 for 32-bit environments described above. This version should support Win95 long filenames. http://www.dbnet.ece.ntua.gr/~george/sed/sed15.exe http://www.cornerstonemag.com/sed/sed15exe.zip 2.2.1.4. MS-DOS sed v1.5 (a/k/a HHsed), by Howard Helman uncompiled source code (Turbo C) ftp://ftp.simtel.net/pub/simtelnet/msdos/txtutl/sed15.zip ftp://ftp.cdrom.com/pub/simtelnet/msdos/txtutl/sed15.zip ftp://oak.oakland.edu/pub/simtelnet/msdos/txtutl/sed15.zip ftp://uiarchive.uiuc.edu/pub/systems/pc/simtelnet/msdos/txtutl/sed15.zip DOS executable and documentation ftp://ftp.simtel.net/pub/simtelnet/msdos/txtutl/sed15x.zip ftp://ftp.cdrom.com/pub/simtelnet/msdos/txtutl/sed15x.zip ftp://oak.oakland.edu/pub/simtelnet/msdos/txtutl/sed15x.zip ftp://uiarchive.uiuc.edu/pub/systems/pc/simtelnet/msdos/txtutl/sed15x.zip sedmod v1.0, by Hern Chen http://www.ptug.org/sed/SEDMOD10.ZIP http://www.cornerstonemag.com/sed/sedmod10.zip ftp://garbo.uwasa.fi/pc/unix/sedmod10.zip CompuServe DTPFORUM, "PC DTP Tools" library, file SEDMOD.ZIP GNU sed v3.02.80 See section 2.2.1.3 ("Microsoft Windows"), above. GNU sed v3.02 See section 2.2.1.3 ("Microsoft Windows"), above. GNU sed v2.05 Does not run under MS-DOS. GNU sed v1.18 32-bit binaries and source, using DJGPP compiler. Requires 80386 SX or better. Also requires 3 CWS*.EXE extenders on the path. See section 5.5 ("What is CSDPMI*B.ZIP and why do I need it?"), below. We recommend using GNU sed v3.02 (above) instead. http://www.simtel.net/pub/simtelnet/gnu/djgpp/v2gnu/sed118b.zip ftp://ftp.cdrom.com/pub/simtelnet/gnu/djgpp/v2gnu/sed118b.zip http://www.simtel.net/pub/simtelnet/gnu/djgpp/v2gnu/sed118s.zip ftp://ftp.cdrom.com/pub/simtelnet/gnu/djgpp/v2gnu/sed118s.zip GNU sed v1.06 16-bit binaries and source. Should run under any MS-DOS system. http://www.simtel.net/pub/simtelnet/gnu/gnuish/sed106.zip ftp://ftp.cdrom.com/pub/simtelnet/gnu/gnuish/sed106.zip 2.2.1.5. CP/M ssed v2.2, by Chuck A. Forsberg http://oak.oakland.edu/pub/cpm/txtutl/ssed22.lbr Written for CP/M, ssed (for "small/stupid stream editor) supports only the a(ppend), c(hange), d(elete) and i(nsert) options, and apparently doesn't support regular expressions. It does have a -u option to "unsqueeze" compressed files and was used mainly in conjunction with dif.com for source code maintenance. change, by Michael M. Rubenstein http://oak.oakland.edu/pub/cpm/txtutl/ttools.lbr Rubenstein probably felt that "sed" was an obscure name, so he renamed it CHANGE.COM (the TTOOLS.LBR archive member CHANGE.CZM is a "crunched" file). Unlike ssed, change supports full RE's except for grouping and backreferences, and its only function is for global substitution. 2.2.2. Shareware and Commercial versions 2.2.2.1. Unix platforms ** Information needed ** 2.2.2.2. OS/2 Hamilton Labs: http://www.hamiltonlabs.com/cshell.htm A sizable set of Unix/C shell utilities designed for OS/2. Price is $350 in the US, $395 elsewhere, with FedEx shipping, unconditional guarantee, unlimited support and free updates. A demo version of the suite can be downloaded from this site, but a stand-alone copy of sed is not available. 2.2.2.3. Windows 95/98, Windows NT, Windows 2000 Hamilton Labs: http://www.hamiltonlabs.com/cshell.htm A sizable set of Unix/C shell utilities designed for Win9x, WinNT, and Win2K. Price is $350 in the US, $395 elsewhere, with FedEx shipping, unconditional guarantee, unlimited support and free updates. A demo version of the suite can be downloaded from this site, but a stand-alone copy of sed is not available. Interix: http://www.interix.com Interix (formerly known as OpenNT) is advertised as "a complete UNIX system environment running natively on Microsoft Windows NT", and is licensed and supported by Softway Systems. It offers over 200 Unix utilities, and supports Unix shells, sockets, networking, and more. A single-user edition runs about $200. A free demo or evaluation copy will run for 31 days and then quit; to continue using it, you must purchase the commercial version. MKS NuTCRACKER Professional http://www.datafocus.com/products/nutc/ A different, yet related product line offered by MKS (Mortice Kern Systems, below); the awkward spelling "NuTCRACKER" is intentional. Various packages offer hundreds of Unix utilities for Win32 environments. Sed is not available as a separate product. UnixDos: http://www.unixdos.com UnixDos is a suite of 82 Unix utilities ported over to the Windows environments. There are 16-bit versions for Win 3.1 and 32-bit versions for WinNT/Win95. It is distributed as uncrippled shareware for the first 30 days. After the test period, the utilities will not run and you must pay the registration fee of $50. Their version of sed supports "\n" in the RHS of expressions, and increases the length of input lines to 10,000 characters. By special arrangement with the owners, persons who want a licensed version of sed *only* (without the other utilities) may pay a license fee of $10. U/WIN: http://www.research.att.com/sw/tools/uwin/ U/WIN is a suite of Unix utilities created for WinNT and Win95 systems. It is owned by AT&T, created by David Korn (author of the Unix korn shell), and is freely distributed only to educational institutions, AT&T employees, or certain researchers; all others must pay a fee after a 90-day evaluation period expires. U/WIN operates best with the NTFS (WinNT file system) but will run in degraded mode with the FAT file system and in further degraded mode under Win95. A minimal installation takes about 25 to 30 megs of disk space. Sed is not available as a separate file for download, but comes with the suite. 2.2.2.4. MS-DOS Mix C/Utilities Toolchest | http://www.mixsoftware.com/product/utility.htm | According to their web page, "The C/Utilities Toolchest adds over | 40 powerful UNIX utilities to your MS-DOS operating system. The | result is an environment very similar to UNIX operating systems, | yet 100% compatible with MS-DOS programs and commands." The | toolchest costs $19.95, with source code available for an | additional fee. Mix C's version of sed is not available separately. | MKS (Mortice Kern Systems) Toolkit http://www.mks.com Sed comes bundled with the MKS Toolkit, which is distributed only as commercial software; it is not available separately. Thompson Automation Software http://www.teleport.com/~thompson/ The Thompson Toolkit contains over 100 familiar Unix utilities, including a version of the Unix Korn shell. It runs under MS-DOS, OS/2, Win 3.0/3.1, Win95, and WinNT. Sed is one of the utilities, though Thompson is better known for its version of awk for DOS, TAWK. The toolkit runs about $150; sed is not available separately. 2.3. Where can I learn to use sed? 2.3.1. Books _Sed & Awk, 2d edition_, by Dale Dougherty & Arnold Robbins (Sebastopol, Calif: O'Reilly and Associates, 1997) ISBN 1-56592-225-5 http://www.oreilly.com/catalog/sed2/noframes.html About 40 percent of this book is devoted to sed, and maybe 50 percent is devoted to awk. The other 10 percent is given to regular expressions and concepts which are common to both tools. If you prefer hard copy, this is definitely the best single place to learn to use sed, including its advanced features. The first edition is also very useful. Several typos crept into the first printing of the first edition (though if you follow the tutorials closely, you'll recognize them right away). A list of errors from the first printing of _sed & awk_ is available at <http://www.cs.colostate.edu/~dzubera/sedawk.txt>, and errors in the 2nd are at <http://www.cs.colostate.edu/~dzubera/sedawk2.txt>, though most of these were corrected in later printings. The second edition tells how POSIX standards have affected these tools and covers the popular GNU versions of sed and awk. Price is about (US) $30.00 ----- _Mastering Regular Expressions_, by Jeffrey E. F. Friedl (Sebastopol, Calif: O'Reilly and Associates, 1997) ISBN 1-56592-257-3 http://www.oreilly.com/catalog/regex/ http://enterprise.ic.gc.ca/~jfriedl/regex/index.html Knowing how to use "regular expressions" is essential to effective use of most Unix tools. This book focuses on how regular expressions can be best implemented in utilities such as perl, vi, emacs, and awk, but also touches on sed as well. Friedl's home page (above) gives links to other sites which help students learn to master regular expressions. His site also gives a Perl script for determining a syntactically valid e-mail address, using regexes: http://enterprise.ic.gc.ca/~jfriedl/regex/email-opt.pl ----- _Awk und Sed_, by Helmut Herold. (Bonn: Addison-Wesley, 1994) ISBN 3-89319-685-4 VVA-Nr. 563-00685-8 The text of this book is in German. Now out of print. ----- _Linux-Unix-Profitools: awk, sed, lex, yacc und make_, by Helumt Herold. (Bonn: Addison-Wesley, 1998) ISBN 3-8273-1448-8 http://www.addison-wesley.de:80/katalog/item.ppml?id=00262 The text of this book is in German. (Comments from German-speaking reviewers appreciated!) 2.3.2. Mailing list The informal "seders" mailing list has changed to a Majordomo mailing list called "sed-users". Regular and digest versions are available. Average mail volume is 12-25 messages per week. For more information, address mail to "majordomo@jpusa.org" with any subject | line and the following in the message body: | info sed-users yourname@your.site | To subscribe, mail to "majordomo@jpusa.org" with any subject line | and one of the following in the message body: | subscribe sed-users yourname@your.site subscribe sed-users-digest yourname@your.site 2.3.3. Tutorials, electronic text The original users manual for sed, by Lee E. McMahon, from the 7th edition UNIX Manual (1978), with the classic "Kubla Khan" example and tutorial, in formatted text format: http://www.urc.bl.ac.yu/manuals/progunix/sed.txt http://www.softlab.ntua.gr/unix/docs/sed.txt The source code to the preceding manual. Use "troff -ms sed" to print this file properly: http://plan9.bell-labs.com/7thEdMan/vol2/sed http://cm.bell-labs.com/7thEdMan/vol2/sed "Do It With Sed", by Carlos Duarte http://www.dbnet.ece.ntua.gr/~george/sed/sedtut_1.html U-SEDIT2.ZIP, by Mike Arst (16 June 1990) http://wuarchive.wustl.edu/systems/ibmpc/garbo.uwasa.fi/editor/u-sedit2.zip ftp://ftp.cs.umu.se/pub/pc/u-sedit2.zip ftp://ftp.uni-stuttgart.de/pub/systems/msdos/util/unixlike/u-sedit2.zip ftp://sunsite.icm.edu.pl/vol/d2/garbo/pc/editor/u-sedit2.zip ftp://ftp.sogang.ac.kr/.1/msdos_garbo/editor/u-sedit2.zip U-SEDIT3.ZIP, by Mike Arst (24 Jan. 1992) http://www.cornerstonemag.com/sed/u-sedit3.zip CompuServe DTPFORUM, "PC DTP Utilities" library, file SEDDOC.ZIP Another sed FAQ http://www.dreamwvr.com/sed-info/sed-faq.html sed-tutorial, by Felix von Leitner http://www.math.fu-berlin.de/~leitner/sed/tutorial.html "Manipulating text with sed," chapter 14 of the SCO OpenServer "Operating System Users Guide" http://dontask.caltech.edu:457/cgi-bin/printchapter/OSUserG/BOOKCHAPTER-14.html http://www.multisoft.it:457/OSUserG/_Manipulating_text_with_sed.html "Combining the Bourne-shell, sed and awk in the UNIX environment for language analysis," by Lothar M. Schmitt and Kiel T. Christianson. This basic tutorial on the Bourne shell, sed and awk downloads as a 71-page PostScript file (compressed to 290K with gzip). You may need to navigate down from the root to get the file. ftp://ftp.u-aizu.ac.jp/u-aizu/doc/Tech-Report/1997/97-2-007.tar.gz available upon request from Lothar Schmitt <lothar@u-aizu.ac.jp> 2.3.4. General web and ftp sites http://seders.icheme.org/ # Casper Boden-Cummins | http://www.cis.nctu.edu.tw/~gis84806/sed/ # Yao-Jen Chang http://www.math.fu-berlin.de/~guckes/sed/ # Sven Guckes http://www.math.fu-berlin.de/~leitner/sed/ # Felix von Leitner http://www.dbnet.ece.ntua.gr/~george/sed/ # Yiorgos Adamopoulos http://www.cornerstonemag.com/sed/ # Eric Pement http://spacsun.rice.edu/FAQ/sed.html ftp://algos.inesc.pt/pub/users/cdua/scripts/sed (Carlos Duarte) ftp://algos.inesc.pt/pub/users/cdua/scripts/sh (sed & shell script) "Handy One-Liners For Sed", compiled by Eric Pement. A large list of 1-line sed commands which can be executed from the command line. http://www.cornerstonemag.com/sed/sed1line.txt http://www.dbnet.ece.ntua.gr/~george/sed/1liners.html The Single UNIX Specification, Version 2 (technical man page) http://www.opengroup.org/onlinepubs/7908799/xcu/sed.html | Getting started with sed http://ftp.uni-klu.ac.at/sed/sed.html Comments in sed http://www.bluesky.com.au:457/OSUserG/_Comments_in_sed.html "Using sed" http://www.multisoft.it:457/OSUserG/_Using_sed_main.html masm to gas converter http://www.delorie.com/djgpp/faq/converting/asm2s-sed.html AltaVista results: "sed script" (744+) http://www.altavista.com/cgi-bin/query?pg=q&kl=XX&stype=stext&q=%22sed+script%22 Google results: "sed script" (668+) http://www.google.com/search?q=%22sed+script%22 HotBot results: "sed script" (190+) http://www.hotbot.com/?MT=%22sed+script%22&SM=MC&DV=0&LG=any&DC=10&DE=2 mail2html.zip http://hiwaay.net/~crispen/src/mail2html.zip customize VIM to aid writing sed scripts http://www.fys.uio.no/~hakonrk/vim/syntax/sed.vim sample uses of sed in batch files and scripts (Benny Pederson) http://users.cybercity.dk/~bse26236/batutil/help/SED.HTM ------------------------------ 3. TECHNICAL 3.1. More detailed explanation of basic sed Sed takes a script of editing commands and applies each command, in order, to each line of input. After all the commands have been applied to the first line of input, that line is output. A second input line is taken for processing, and the cycle repeats. Sed scripts can address a single line by line number or by matching a /RE pattern/ on the line. An exclamation mark '!' after a regex ('/RE/!') or line number will select all lines that do NOT match that address. Sed can also address a range of lines in the same manner, using a comma to separate the 2 addresses. $d # delete the last line of the file /[0-9]\{3\}/p # print lines with 3 consecutive digits 5!s/ham/cheese/ # except on line 5, replace 'ham' with 'cheese' /awk/!s/aaa/bb/ # unless 'awk' is found, replace 'aaa' with 'bb' 17,/foo/d # delete all lines from line 17 up to 'foo' Following an address or address range, sed accepts curly braces '{...}' so several commands may be applied to that line or to the lines matched by the address range. On the command line, semicolons ';' separate each instruction and must precede the closing brace. sed '/Owner:/{s/yours/mine/g;s/your/my/g;s/you/me/g;}' file Range addresses operate differently depending on which version of sed is used (see section 6.8.5, below). For further information on using sed, consult the references in section 2.3, above. The online manual ("man pages") on Unix/Linux systems may be helpful (try "man sed"), but man pages are notoriously obscure for first-time users. 3.2. Common one-line sed scripts A separate document of over 70 handy "one-line" sed commands is available at <http://www.cornerstonemag.com/sed/sed1line.txt>. Here are fourteen of the most common sed commands for one-line use. MS-DOS users should replace single quotes ('...') with double quotes ("...") in these examples. A specific filename ("file") usually follows the script, though the input may also come via piping ("sort somefile | sed 'somescript'"). # 1. Double space a file sed G file # 2. Triple space a file sed 'G;G' file # 3. Under UNIX: convert DOS newlines (CR/LF) to Unix format sed 's/.$//' file # assumes that all lines end with CR/LF sed 's/^M$// file # in bash/tcsh, press Ctrl-V then Ctrl-M # 4. Under DOS: convert Unix newlines (LF) to DOS format sed 's/$//' file # method 1 sed -n p file # method 2 # 5. Delete leading whitespace (spaces/tabs) from front of each line # (this aligns all text flush left). '^t' represents a true tab # character. Under bash or tcsh, press Ctrl-V then Ctrl-I. sed 's/^[ ^t]*//' file # 6. Delete trailing whitespace (spaces/tabs) from end of each line sed 's/[ ^t]*$//' file # see note on '^t', above # 7. Delete BOTH leading and trailing whitespace from each line sed 's/^[ ^t]*//;s/[ ^]*$//' file # see note on '^t', above # 8. Substitute "foo" with "bar" on each line sed 's/foo/bar/' file # replaces only 1st instance in a line sed 's/foo/bar/4' file # replaces only 4th instance in a line sed 's/foo/bar/g' file # replaces ALL instances within a line # 9. Substitute "foo" with "bar" ONLY for lines which contain "baz" sed '/baz/s/foo/bar/g' file # 10. Delete all CONSECUTIVE blank lines from file except the first. # This method also deletes all blank lines from top and end of file. # (emulates "cat -s") sed '/./,/^$/!d' file # this allows 0 blanks at top, 1 at EOF sed '/^$/N;/\n$/D' file # this allows 1 blank at top, 0 at EOF # 11. Delete all leading blank lines at top of file (only). sed '/./,$!d' file # 12. Delete all trailing blank lines at end of file (only). sed -e :a -e '/^\n*$/{$d;N;};/\n$/ba' file | # 13. If a line ends with a backslash, join the next line to it. sed -e :a -e '/\\$/N; s/\\\n//; ta' file # 14. If a line begins with an equal sign, append it to the # previous line (and replace the "=" with a single space). sed -e :a -e '$!N;s/\n=/ /;ta' -e 'P;D' file 3.3. Addressing and address ranges Sed commands may have an optional "address" or "address range" prefix. If there is no address or address range given, then the command is applied to all the lines of the input file or text stream. Three commands cannot take an address prefix: - labels, used to branch or jump within the script - the close brace, '}', which ends the '{' "command" - the '#' comment character, also technically a "command" An address can be a line number (such as 1, 5, 37, etc.), a regular expression (written in the form /RE/ or \xREx where 'x' is any character other than '\' and RE is the regular expression), or the dollar sign ($), representing the last line of the file. An exclamation mark (!) after an address or address range will apply the command to every line EXCEPT the ones named by the address. A null regex ("//") will be replaced by the last regex which was used. Also, some seds do not support \xREx as regex delimiters. 5d # delete line 5 only 5!d # delete every line except line 5 /RE/s/LHS/RHS/g # substitute only if RE occurs on the line /^$/b label # if the line is blank, branch to ':label' /./!b label # ... another way to write the same command \%.%!b label # ... yet another way to write this command $!N # on all lines but the last, get the Next line Note that an embedded newline can be represented in an address by the symbol \n, but this syntax is needed only if the script puts 2 or more lines into the pattern space via the N, G, or other commands. The \n symbol does *not* match the newline at an end-of-line because when sed reads each line into the pattern space for processing, it strips off the trailing newline, processes the line, and adds a newline back when printing the line to standard output. To match the end-of-line, use the '$' metacharacter, as follows: /tape$/ # matches the word 'tape' at the end of a line /tape$deck/ # matches the word 'tape$deck' with a literal '$' /tape\ndeck/ # matches 'tape' and 'deck' with a newline between The following sed commands usually accept *only* a single address. All other commands (except labels, '}', and '#') accept both single addresses and address ranges. = print to stdout the line number of the current line a after printing the current line, append "text" to stdout i before printing the current line, insert "text" to stdout q quit after the current line is matched r file prints contents of "file" to stdout after line is matched Note that we said "usually." If you need to apply the '=', 'a', 'i', or 'r' commands to each and every line within an address range, this behavior can be coerced by the use of braces. Thus, "1,9=" is an invalid command, but "1,9{=;}" will print each line number followed by its line for the first 9 lines (and then print the rest of the rest of the file normally). Address ranges occur in the form <address1>,<address2> or <address1>,<address2>! where the address can be a line number or a standard /regex/. <address2> can also be a dollar sign, indicating the end of file. Under HHsed and gsed302a, <address2> may also be a notation of the form +num, indicating the next _num_ lines after <address1> is matched. Address ranges are: (1) Inclusive. The range "/From here/,/eternity/" matches all the lines containing "From here" up to and including the line containing "eternity". It will not stop on the line just prior to "eternity". (If you don't like this, see section 4.15.) (2) Plenary. They always match full lines, not just parts of lines. In other words, a command to change or delete an address range will change or delete whole lines; it won't stop in the middle of a line. (3) Multilinear. Address ranges normally match 2 lines or more. The second address will never match the same line the first address did; therefore a valid address range always spans at least two lines, with these exceptions which match only one line: - if the first address matches the last line of the file - if using the syntax "/RE/,3" and /RE/ occurs only once in the file at line 3 or below - if using HHsed v1.5. See section 6.8.5. (4) Minimalist. In address ranges with /regex/ as <address2>, the range "/foo/,/bar/" will stop at the first "bar" it finds, provided that "bar" occurs on a line below "foo". If the word "bar" occurs on several lines below the word "foo", the range will match all the lines from the first "foo" up to the first "bar". It will not continue hopping ahead to find more "bar"s. In other words, address ranges are not "greedy," like regular expressions. (5) Repeating. An address range will try to match more than one block of lines in a file. However, the blocks cannot nest. In addition, a second match will not "take" the last line of the previous block. For example, given the following text, start stop start stop the sed command '/start/,/stop/d' will only delete the first two lines. It will not delete all 3 lines. (6) Relentless. If the address range finds a "start" match but doesn't find a "stop", it will match every line from "start" to the end of the file. Thus, beware of the following behaviors: /RE1/,/RE2/ # if /RE2/ is not found, matches from /RE1/ to the # end-of-file 20,/RE/ # if /RE/ is not found, matches from line 20 to the # end-of-file /RE/,30 # if /RE/ occurs any time after line 30, each # occurrence will be matched in HHsed, sedmod, and # gsed302. GNU sed v2.05 and 1.18 will match from # the 2nd occurrence of /RE/ to the end-of-file. If these behaviors seem strange, remember that they occur because sed does not look "ahead" in the file. Doing so would stop sed from being a stream editor and have adverse effects on its efficiency. If these behaviors are undesirable, they can be circumvented or corrected by the use of nested testing within braces. The following scripts work under GNU sed 3.02: # Execute your_commands on range "/RE1/,/RE2/", but if /RE2/ is # not found, do nothing. /RE1/{:a;N;/RE2/!ba;your_commands;} # Execute your_commands on range "20,/RE/", but if /RE/ is not # found, do nothing. 20{:a;N;/RE/!ba;your_commands;} As a side note, once we've used N to "slurp" lines together to test for the ending expression, the pattern space will have gathered many lines (possibly thousands) together and concatenated them as a single expression, with the \n sequence marking line breaks. The REs *within* the pattern space may have to be modified (e.g., you must write '/\nStart/' instead of '/^Start/' and '/[^\n]*/' instead of '/.*/') and other standard sed commands will be unavailable or difficult to use. # Execute your_commands on range "/RE/,30", but if /RE/ occurs # on line 31 or later, do not match it. 1,30{/RE/,$ your_commands;} For related suggestions on using address ranges, see sections 4.2, 4.15, and 4.19 of this FAQ. Note that HHsed contains a bug or nonstandard feature in how it implements address ranges; also, GNU sed 3.02a supports a zero (0) in addressing. For more details, see section 6.8.5 ("Range addressing with GNU sed and HHsed"). 3.4. [reserved] 3.5. [reserved] 3.6. Notes about s2p, the sed-to-perl translator s2p (sed to perl) is a Perl program to convert sed scripts into the Perl programming language; it is included with many versions of Perl. These problems have been found when using s2p: (1) Doesn't recognize the semicolon properly after s/// commands. s/foo/bar/g; (2) Doesn't trim trailing whitespace after s/// commands. Even lone trailing spaces, without comments, produce an error. (3) Doesn't handle multiple commands within braces. E.g., 1,4{=;G;} will produce perl code with missing braces, and miss the second "G" command as well. In fact, any commands after the first one are missed in the perl output script, and the output perl script will also contain mismatched braces. 3.7. GNU/POSIX extensions to regular expressions GNU sed supports "character classes" in addition to regular character sets, such as [0-9A-F]. Like regular character sets, character classes represent any single character within a set. "Character classes are a new feature introduced in the POSIX standard. A character class is a special notation for describing lists of characters that have a specific attribute, but where the actual characters themselves can vary from country to country and/or from character set to character set. For example, the notion of what is an alphabetic character differs in the USA and in France." [quoted from the docs for GNU awk v3.0.3] Though character classes don't generally conserve space on the line, they help make scripts portable for international use. The equivalent character sets *for U.S. users* follow: [[:alnum:]] - [A-Za-z0-9] Alphanumeric characters [[:alpha:]] - [A-Za-z] Alphabetic characters [[:blank:]] - [ \x09] Space or tab characters only [[:cntrl:]] - [\x00-\x19\x7F] Control characters [[:digit:]] - [0-9] Numeric characters [[:graph:]] - [!-~] Printable and visible characters [[:lower:]] - [a-z] Lower-case alphabetic characters [[:print:]] - [ -~] Printable (non-Control) characters [[:punct:]] - [!-/:-@[-`{-~] Punctuation characters [[:space:]] - [ \t\v\f] All whitespace chars [[:upper:]] - [A-Z] Upper-case alphabetic characters [[:xdigit:]] - [0-9a-fA-F] Hexadecimal digit characters Note that [[:graph:]] does not match the space " ", but [[:print:]] does. Some character classes may (or may not) match characters in the high ASCII range (ASCII 128-255 or 0x80-0xFF), depending on which C library was used to compile sed. For non-English languages, [[:alpha:]] and other classes may also match high ASCII characters. ------------------------------ 4. EXAMPLES 4.1. How do I perform a case-insensitive search? Use GNU sed v3.02 (or higher) with the I flag ("/regex/I" or "s/LHS/RHS/I"). Or use sedmod with the -i switch on the command line. With other versions of sed this is not easy to do, so some people use GNU awk (gawk), mawk, or perl, since these programs have options for case-insensitive searches. In gawk/mawk, use "BEGIN {IGNORECASE=1}" and in perl, "/regex/i". For sed, here are three solutions: Solution 1: convert everything to upper case and search normally # sed script, solution 1 h; # copy the original line to the hold space # convert the pattern space to solid caps y/abcdefghijklmnopqrstuvwxyz/ABCDEFGHIJKLMNOPQRSTUVWXYZ/ # now we can search for the word "CARLOS" /CARLOS/ { # add or insert lines. Note: "s/.../.../" will not work # here because we are searching a modified pattern # space and are not printing the pattern space. } x; # get back the original pattern space # the original pattern space will be printed Solution 2: search for both cases Often, proper names will either start with all lower-case ("unix"), with an initial capital letter ("Unix") or occur in solid caps ("UNIX"). There may be no need to search for every possibility. /UNIX/b match /[Uu]nix/b match Solution 3: search for all possible cases # If all else fails, search for any possible combination /[Ca][Aa][Rr][Ll][Oo][Ss]/... Bear in mind that as the pattern length increases, this solution becomes an order of magnitude slower than the one of Solution 1, at least with some implementations of sed. 4.2. How do I make changes in only part of a file? Select parts of a file for changing by naming a range of lines either by number (e.g., lines 1-20), by RE (between the words "foo" and "bar"), or by some combination of the two. For multiple changes, put the substitution command between braces {...}. # replace only between lines 1 and 20 1,20 s/Johnson/White/g # replace everywhere EXCEPT between lines 1 and 20 1,20 !s/Johnson/White/g # replace only between words "foo" and "bar" /foo/,/bar/ { s/Johnson/White/g; s/Smith/Wesson/g; } # replace only from the words "ENDNOTES:" to the end of file /ENDNOTES:/,$ { s/Schaff/Herzog/g; s/Kraft/Ebbing/g; } For technical details on using address ranges, see section 3.3 ("Addressing and Address ranges"). 4.3. How do I change only the first occurrence of a pattern? To replace the regex "LHS" with "RHS", do this: gsed '0,/LHS/s//RHS/' # GNU sed 3.02a sed -e '1s/LHS/RHS/;t' -e '1,/LHS/s//RHS/' # other seds If you know the pattern *won't* occur on the first line, omit the first -e and the statement following it. 4.4. How do I make substitutions in every file in a directory, or in a complete directory tree? 4.4.1. - Perl solution (Yes, we know this is a FAQ file for sed, not perl, but the solution is so simple that it has to be noted. Also, perl and sed share a very similar syntax here.) perl -pi.bak -e 's|foo|bar|g' filelist # or perl -pi.bak -e 's|foo|bar|g' `find /pathname -name "filespec"` For each file in the filelist, perl renames the source file to "filename.bak"; the modified file gets the original filename. Change '-pi.bak' to '-pi' if you don't need backup copies. (Note the use of s||| instead of s/// here, and in the scripts below. The vertical bars in the 's' command lets you replace '/some/path' with '/another/path', accommodating slashes in the LHS and RHS.) 4.4.2. - Unix solution For all files in a single directory, assuming they end with *.txt and you have no files named "[anything].txt.bak" already, use a shell script: #! /bin/sh # Source files are saved as "filename.txt.bak" in case of error # The '&&' after cp is an additional safety feature for file in *.txt do cp $file $file.bak && sed 's|foo|bar|g' $file.bak >$file done To do an entire directory tree, use the Unix utility find, like so (thanks to Jim Dennis <jadestar@rahul.net> for this script): #! /bin/sh # filename: replaceall find . -type f -name '*.txt' -print | while read i do sed 's|foo|bar|g' $i > $i.tmp && mv $i.tmp $i done This previous shell script recurses through the directory tree, finding only files in the directory (not symbolic links, which will be encountered by the shell command "for file in *.txt", above). To preserve file permissions and make backup copies, use the 2-line cp routine of the earlier script instead of "sed ... && mv ...". By replacing the sed command 's|foo|bar|g' with something like sed "s|$1|$2|g" ${i}.bak > $i using double quotes instead of single quotes, the user can also employ positional parameters on the shell script command tail, thus reusing the script from time to time. For example, replaceall East West would modify all your *.txt files in the current directory. 4.4.3. - DOS solution: MS-DOS users should use two batch files like this: @echo off :: MS-DOS filename: REPLACE.BAT :: :: Create a destination directory to put the new files. :: Note: The next command will fail under Novel Netware :: below version 4.10 unless "SHOW DOTS=ON" is active. if not exist .\NEWFILES\NUL mkdir NEWFILES for %%f in (*.txt) do CALL REPL_2.BAT %%f echo Done!! :: =======End of the first batch file==== @echo off :: MS-DOS filename: REPL_2.BAT :: sed "s/foo/bar/g" %1 > NEWFILES\%1 :: =======End of the second batch file=== When finished, the current directory contains all the original files, and the newly-created NEWFILES subdirectory contains the modified *.TXT files. Do not attempt a command like for %%f in (*.txt) do sed "s/foo/bar/g" %%f >NEWFILES\%%f under any version of MS-DOS because the output filename will be created as a literal '%f' in the NEWFILES directory before the %%f is expanded to become each filename in (*.txt). This occurs because MS-DOS creates output filenames via redirection commands before it expands "for..in..do" variables. To recurse through an entire directory tree in MS-DOS requires a batch file more complex than we have room to describe. Examine the file SWEEP.BAT in Timo Salmi's great archive of batch tricks, TSBAT61.ZIP, located at <ftp://garbo.uwasa.fi/pc/ts/tsbat61.zip>, | or get an external program designed for directory recursion. Here | are some recommended programs for directory recursion. The first | one, FORALL, runs under either OS/2 or DOS. Unfortunately, none of | these supports Win9x long filenames. | ftp://hobbes.nmsu.edu/pub/os2/util/disk/forall72.zip | http://www.geocities.com/SiliconValley/Lakes/2414/fortn711.zip http://garbo.uwasa.fi/pc/filefind/target15.zip 4.5. How do I parse a comma-delimited data file? Comma-delimited data files can come in several forms, requiring increasing levels of complexity in parsing and handling: (a) No quotes, no internal commas 1001,John Smith,PO Box 123,Chicago,IL,60699 1002,Mary Jones,320 Main,Denver,CO,84100, (b) Like (a), with quotes around each field "1003","John Smith","PO Box 123","Chicago","IL","60699" "1004","Mary Jones","320 Main","Denver","CO","84100" (c) Like (b), with embedded commas "1005","Tom Hall, Jr.","61 Ash Ct.","Niles","OH","44446" "1006","Bob Davis","429 Pine, Apt. 5","Boston","MA","02128" (d) Like (c), with embedded commas and quotes "1007","Sue "Red" Smith","19 Main","Troy","MI","48055" "1008","Joe "Hey, guy!" Hall","POB 44","Reno","NV","89504" In each example above, we have 7 fields and 6 commas which function as field separators. Case (c) is a very typical form of these data files, with double quotes used to enclose each field and to protect internal commas (such as "Tom Hall, Jr.") from interpretation as field separators. However, many times the data may include both embedded quotation marks as well as embedded commas, as seen by case (d), above. Before handling a comma-delimited data file, make sure that you fully understand its format and check the integrity of the data. Does each line contain the same number of fields? Should certain fields be composed only of numbers or of two-letter state abbreviations in all caps? Sed (or awk or perl) should be used to validate the integrity of the data file before you attempt to alter it or extract particular fields from the file. After ensuring that each line has a valid number of fields, use sed to locate and modify individual fields, using the \(...\) grouping command where needed. In case (a): sed 's/^[^,]*,[^,]*,[^,]*,[^,]*,/.../' ^ ^ ^ | | |_ 3rd field | |_______ 2nd field |_____________ 1st field # Unix script to delete the second field for case (a) sed 's/^\([^,]*\),[^,]*,/\1,,/' file # Unix script to change field 1 to 9999 for case (a) sed 's/^[^,]*,/9999,/' file In cases (b) and (c): sed 's/^"[^"]*","[^"]*","[^"]*","[^"]*",/.../' 1st-- 2nd-- 3rd-- 4th-- # Unix script to delete the second field for case (c) sed 's/^\("[^"]*"\),"[^"]*",/\1,"",/' file # Unix script to change field 1 to 9999 for case (c) sed 's/^"[^"]*",/"9999",/' file In case (d): One way to parse such files is to replace the 3-character field separator "," with an unused character like the tab or vertical bar. (Technically, the field separator is only the comma while the fields are surrounded by "double quotes", but the net _effect_ is that fields are separated by quote-comma-quote, with quote characters added to the beginning and end of each record.) Search your datafile _first_ to make sure that your character appears nowhere in it! sed -n '/|/p' file # search for any instance of '|' # if it's not found, we can use the '|' to separate fields Then replace the 3-character field separator and parse as before: # sed script to delete the second field for case (d) s/","/|/g; # global change of "," to bar s/^\([^|]*\)|[^|]|/\1||/; # delete 2nd field s/|/","/g; # global change of bar back to "," # sed script to change field 1 to 9999 for case (d) # Remember to accommodate leading and trailing quote marks s/","/|/g; s/^[^|]*|/"9999|/; s/|/","/g; Note that this technique works only if _each_ and _every_ field is surrounded with double quotes, including empty fields. If your datafile does not look like case (d), above, or if it omits quote marks around empty fields or numeric values, then the complexity of the script would probably not be worth the effort to write it in sed. For such a case, you should use perl. This question is addressed in the Perl FAQ, at question 4.28: "How can I split a [character] delimited string except when inside [character]?" 4.6. How do I insert a newline into the RHS of a substitution? Six versions of sed permit '\n' to be typed directly into the RHS, which is then converted to a newline on output: gsed-3.02.80, gsed-3.02a, gsed103 (with the -x switch), HHsed (a/k/a sed14), sedmod, and UnixDOS sed. The _easiest_ solution is to use one of these versions. For other versions of sed, try one of the following: (a) Insert an unused character and pipe the output through tr: echo twolines | sed 's/two/& new=/' | tr "=" "\n" # produces two new lines (b) Use two backslashes (\\) from the shell prompt. Using bash: [bash-prompt]$ echo twolines | sed "s/two/& new\\ >/" two new lines [bash-prompt]$ (c) Write a multi-line script and use the backslash (\) in the middle of the "replace" portion: sed -f newline.sed files # newline.sed s/twolines/two new\ lines/g Some versions of sed may not need the trailing backslash. If so, remove it. (d) Use the "G" command: G appends a newline, plus the contents of the hold space to the end of the pattern space. If the hold space is empty, a newline is appended anyway. The newline is stored in the pattern space as "\n" where it can be addressed by grouping "\(...\)" and moved in the RHS. Thus, to change the "twolines" example used earlier, the following script will work: sed '/twolines/{G;s/\(two\)\(lines\)\(\n\)/\1\3\2/;}' (e) Inserting full lines, not breaking lines up: If one is not *changing* lines but only inserting complete lines before or after a pattern, the procedure is much easier. Use the "i" (insert) or "a" (append) command, making the alterations by an external script. To insert "This line is new" BEFORE each line matching a regex: /RE/i This line is new # HHsed, sedmod, gsed 3.02a /RE/{x;s/.*/This line is new/;G;} # other seds To append "This line is new" AFTER each line matching a regex: /RE/a This line is new # HHsed, sedmod, gsed 3.02a /RE/{G;s/$/This line is new/;} # other seds To append 2 blank lines after each line matching a regex: /RE/{G;G;} # assumes the hold space is empty To replace each line matching a regex with 5 blank lines: /RE/{s/.*//;G;G;G;G;} # assumes the hold space is empty (f) Use the "y///" command if possible: On some Unix versions of sed (not GNU sed!), though the s/// command won't accept '\n' in the RHS, the y/// command does. If your Unix sed supports it, a newline after "aaa" can be inserted this way (which is not portable to GNU sed or other seds): s/aaa/&~/; y/~/\n/; # assuming no other '~' is on the line! 4.7. How do I represent control-codes or nonprintable characters? GNU sed v3.02.80, GNU sed v1.03, and HHsed v1.5 by Howard Helman all support all support the notation \xNN, where "NN" are two valid hex numbers, 00-FF. sed is not intended to process binary or object code, and files which contain nulls (0x00) will usually generate errors in most versions of sed (GNU sed 3.02a is an exception; it allows nulls in the input files and also in regexes). On Unix platforms, the 'echo' command may allow insertion of octal or hex values, e.g., `echo "\0nnn"` or `echo -n "\0nnn"`. The echo command may also support syntax like '\\b' or '\\t' for backspace or tab characters. Check the man pages to see what syntax your version of echo supports. Some versions support the following: # replace 0x1A (32 octal) with ASCII letters sed 's/'`echo "\032"`'/Ctrl-Z/g' # note the 3 backslashes in the command below sed "s/.`echo \\\b`//g" 4.8. How do I read environment variables with sed? 4.8.1. - on Unix platforms In Unix, environment variables are words which begin with a dollar sign, such as $TERM, $HOME, $user, or $path. In sed, the dollar sign is used to indicate the last line of the input file, the end of a line (in the LHS), or a literal symbol (in the RHS). Sed cannot access variables directly, so one must pay attention to shell quoting requirements to expand the variables properly. To ALLOW the Unix shell to interpret the dollar sign (replacing it with an environment variable), put the script in double quotes: sed "s/_terminal-type_/$TERM/g" input.file >output.file To PREVENT the Unix shell from interpreting the dollar sign (letting sed define its meaning), put the script in single quotes: sed 's/.$//' DOS.file >Unix.file To use BOTH Unix $environment_vars and sed /end-of-line$/ pattern matching, use single quotes to bracket the sed part 'like so', then follow immediately with double quotes "$HERE" when you want the shell to substitute the variable, and resume with single quotes again where 'sed should set the meaning'. There must be NO SPACE between the closing single quotes and the opening double quotes. To demonstrate with the example two sentences above: sed 'like so'"$HERE"'sed should set the meaning' # rough idea sed "s/$user"'$/root/' input.file >output.file # sample use In the sample use above, we search for the user's name (which is stored as an environment variable) when it occurs at the end of the line ($), and we substitute the word "root" in all these occasions. In writing shell scripts, we likewise begin with single quote marks ('), close them upon encountering the variable, enclose the variable name in double quotes ("), and resume with single quotes, closing them at the end of the sed script. Example: #! /bin/sh # lower to upper, that could be changed FROM='abcdefgh' TO='ABCDEFGH' ... misc commands that pipe data into a longer sed script. sed ' ... # do the conversion y/'"$FROM"'/'"$TO"'/ # some more commands go here . . . # last line is a single quote mark ' Thus, each variable named $FROM is replaced by $TO, and the single quotes are used to glue the multiple lines together in the script. (See also section 4.10, "How do I handle shell quoting in sed?") 4.8.2. - on MS-DOS and 4DOS platforms Under 4DOS and MS-DOS version 7.0 (Win95) or 7.10 (Win95 OSR2), environment variables can be accessed from the command prompt. Under MS-DOS 6.22 and below, environment variables can only be accessed from within batch files. Environment variables should be enclosed between percent signs and are case-insensitive; i.e., %USER% or %user% will display the USER variable. To generate a true percent sign, just enter it twice. DOS versions of sed require that sed scripts be enclosed by double quote marks "..." (not single quotes!) if the script contains embedded tabs, spaces, redirection arrows or the vertical bar. In fact, if the input for sed comes from piping, a sed script should not contain a vertical bar, even if it is protected by double quotes (this seems to be bug in the normal MS-DOS syntax). Thus, echo blurk | sed "s/^/ |foo /" # will cause an error sed "s/^/ |foo /" blurk.txt # will work as expected Using DOS environment variables which contain DOS path statements (such as a TMP variable set to "C:\TEMP") within sed scripts is discouraged because sed will interpret the backslash '\' as a metacharacter to "quote" the next character, not as a normal symbol. Thus, sed "s/^/%TMP% /" somefile.txt will not prefix each line with (say) "C:\TEMP ", but will prefix each line with "C:TEMP "; sed will discard the backslash, which is probably not what you want. Other variables such as %PATH% and %COMSPEC% will also lose the backslash within sed scripts. Environment variables which do not use backslashes are usually workable. Thus, all the following should work without difficulty, if they are invoked from within DOS batch files: sed "s/=username=/%USER%/g" somefile.txt echo %FILENAME% | sed "s/\.TXT/.BAK/" grep -Ei "%string%" somefile.txt | sed "s/^/ /" while from either the DOS prompt or from within a batch file, sed "s/%%/ percent/g" input.fil >output.fil will replace each percent symbol in a file with " percent" (adding the leading space for readability). 4.9. How do I export or pass variables back into the environment? 4.9.1. - on Unix platforms Suppose that line #1, word #2 of the file 'terminals' contains a value to be put in your TERM environment variable. Sed cannot export variables directly to the shell, but it can pass strings to shell commands. To set a variable in the Bourne shell: TERM=`sed 's/^[^ ][^ ]* \([^ ][^ ]*\).*/\1/;q' terminals`; export TERM If the second word were "Wyse50", this would send the shell command "TERM=Wyse50". 4.9.2. - on MS-DOS or 4DOS platforms Sed cannot directly manipulate the environment. Under DOS, only batch files (.BAT) can do this, using the SET instruction, since they are run directly by the command shell. Under 4DOS, special 4DOS commands (such as ESET) can also alter the environment. Under DOS or 4DOS, sed can select a word and pass it to the SET command. Suppose you want the 1st word of the 2nd line of MY.DAT put into an environment variable named %PHONE%. You might do this: @echo off sed -n "2 s/^\([^ ][^ ]*\) .*/SET PHONE=\1/p;3q" MY.DAT > GO_.BAT call GO_.BAT echo The environment variable for PHONE is %PHONE% :: cleanup del GO_.BAT The sed script assumes that the first character on the 2nd line is not a space and uses grouping \(...\) to save the first string of non-space characters as \1 for the RHS. In writing any batch files, make sure that output filenames such as GO_.BAT don't overwrite preexisting files of the same name. 4.10. How do I handle Unix shell quoting in sed? To embed a literal single quote (') in a script, use (a) or (b): (a) If possible, put the script in double quotes: sed "s/cannot/can't/g" file (b) If the script must use single quotes, then close-single-quote the script just before the SPECIAL single quote, prefix the single quote with a backslash, and use a 2nd pair of single quotes to finish marking the script. Thus: sed 's/cannot$/can'\''t/g' file Though this looks hard to read, it breaks down to 3 parts: 's/cannot$/can' \' 't/g' --------------- -- ----- To embed a literal double quote (") in a script, use (a) or (b): (a) If possible, put the script in single quotes. You don't need to prefix the double quotes with anything. Thus: sed 's/14"/fourteen inches/g' file (b) If the script must use double quotes, then prefix the SPECIAL double quote with a backslash (\). Thus, sed "s/$length\"/$length inches/g" file To embed a literal backslash (\) into a script, enter it twice: sed 's/C:\\DOS/D:\\DOS/g' config.sys 4.11. How do I delete a block of text if the block contains a certain regular expression? The following deletes the block between 'start' and 'end' inclusively, if and only if the block contains the string (optionally a pattern) 'regex'. Written by Russell Davies <r@itntl.bhp.com.au>, with comments by the FAQ maintainer: :t /start/,/end/ { # For each line between these block markers.. /end/!{ # If we are not at the /end/ marker $!{ # nor the last line of the file, | N; # add the Next line to the pattern space bt } # and branch (loop back) to the :t label. } # This line matches the /end/ marker. | /regex/d; # If /regex/ matches, delete the block. | } # Otherwise, the block will be printed. 4.12. How do I locate/print a paragraph of text if the paragraph contains a certain regular expression? Assume that paragraphs are separated by blank lines. For regexes that are single terms, use the following script: sed -e '/./{H;$!d;}' -e 'x;/regex/!d' To print paragraphs only if they contain 3 specific regular expressions (RE1, RE2, and RE3), in any order in the paragraph: sed -e '/./{H;$!d;}' -e 'x;/RE1/!d;/RE2/!d;/RE3/!d' With this solution and the preceding one, if the paragraphs are excessively long (more than 4k in length), you may overflow sed's internal buffers. If using HHsed, you must add a "G;" command immediately after the "x;" in the scripts above to defeat a bug in HHsed (see section 6.7.F(5), below, for a description). 4.13. How do I delete a block of _specific_ consecutive lines? If the block of lines always looks like this (with '^' and '$' representing the beginning and end of line, respectively): ^able$ ^baker$ ^charlie$ ^delta$ and if there is never any deviation from this format (e.g., "able" *always* is followed by "baker", etc.), this will work fine: sed '/^able$/,/^delta$/d' files # most seds sed '/^able$/,+3d' files # HHsed, sedmod, gsed 3.02.80 However, if the top line sometimes appears alone or is followed by other lines, if the block may have additional lines in the middle, or if a partial block could possibly occur somewhere in the file, a more explicit script is needed. The following scripts show how to delete blocks of specific consecutive lines. Only an exact match of the block is deleted, and partial matches of the block are left alone. # sed script to delete 2 consecutive lines: /^RE1\nRE2$/ $b /^RE1$/ { $!N /^RE1\nRE2$/d P;D } #---end of script--- # sed script to delete 3 consecutive lines. (This script # fails under GNU sed earlier than version 3.02.) : more $!N s/\n/&/2; t enough $!b more : enough /^RE1\nRE2\nRE3$/d P;D #---end of script--- For example, to delete a block of 5 consecutive lines, the previous script must be altered in only two places: (1) Change the 2 in "s/\n/&/2;" to a 4 (the trailing semicolon is needed to work around a bug in HHsed v1.5). (2) Change the regex line to "/^RE1\nRE2\nRE3\nRE4\nRE5$/d", modifying the expression as needed. Suppose we want to delete a block of two blank lines followed by the word "foo" followed by another blank line (4 lines in all). Other blank lines and other instances of "foo" should be left alone. After changing the '2' to a '3' (always one number less than the total number of lines), the regex line would look like this: "/^\n\nfoo\n$/d". (Thanks to Greg Ubben for this script.) As an alternative for older versions of GNU sed, the following script will delete 4 consecutive lines: # sed script to delete 4 consecutive lines (gsed-2.05 and below) /^RE1$/!b $!N $!N :a $b N /^RE1\nRE2\nRE3\nRE4$/d P s/^.*\n\(.*\n.*\n.*\)$/\1/ ba #---end of script--- Its drawback is that it must be modified in 3 places instead of 2 to adapt it for more lines, and as additional lines are added, the 's' command is forced to work harder to match the regexes. On the other hand, it avoids a problem with gsed-2.05 and shows another way to solve the problem of deleting consecutive lines. 4.14. How do I read (insert/add) a file at the top of a textfile? Given a textfile, file1, one may wish to prepend or insert an external file, fileT, to the top of it before processing the file. Normally, this should be done from the Unix or DOS shell before passing file1 on to sed (MS-DOS 5.0 or lower needs 3 commands to do this; for DOS 6.0 or higher, the MOVE command is available): copy fileT+file1 temp # MS-DOS command 1 echo Y | copy temp file1 # MS-DOS command 2 del temp # MS-DOS command 3 cat fileT file1 >temp; mv temp file1 # Unix commands However, if inserting the file must be done from within sed, there is a way. The expected sed command "1 r fileT" will not work; it first prints line 1 and then inserts fileT between lines 1 and 2. The following two-line sed script solves this problem, although there must be at least 2 lines in file1 for the script to work properly: 1{ h; r fileT; D; } 2{ x; G; } 4.15. How do I address all the lines between RE1 and RE2, excluding the lines themselves? Normally, to address the lines between two regular expressions, RE1 and RE2, one would do this: '/RE1/,/RE2/{commands;}'. Excluding those lines takes an extra step. To put 2 arrows before each line between RE1 and RE2, except for those lines: sed '1,/RE1/!{ /RE2/,/RE1/!s/^/>>/; }' input.fil The preceding script, though short, may be difficult to follow. It also requires that /RE1/ cannot occur on the first line of the input file. The following script, though it's not a one-liner, is easier to read and it permits /RE1/ to appear on the first line: /RE1/,/RE2/{ /RE1/b /RE2/b s/^/>>/ } Contents of input.fil: Output of sed script: aaa aaa bbb bbb RE1 RE1 aaa >>aaa bbb >>bbb ccc >>ccc RE2 RE2 end end 4.16. How do I replace "/some/UNIX/path" in a substitution? Technically, the normal meaning of the slash can be disabled by prefixing it with a backslash. Thus, sed 's/\/some\/UNIX\/path/\/a\/new\/path/g' files But this is hard to read and write. There is a better solution. The s/// substitution command allows '/' to be replaced by any other character (including spaces or alphanumerics). Thus, sed 's|/some/UNIX/path|/a/new/path|g' files and if you are using variable names in a Unix shell script, sed "s|$OLDPATH|$NEWPATH|g" oldfile >newfile 4.17. How do I replace "C:\SOME\DOS\PATH" in a substitution? For MS-DOS users, every backslash must be doubled. Thus, to replace "C:\SOME\DOS\PATH" with "D:\MY\NEW\PATH" -- sed "s|C:\\SOME\\DOS\\PATH|D:\\MY\\NEW\\PATH|g" infile >outfile Remember that DOS pathnames are not case sensitive and can appear in upper or lower case in the input file. If this concerns you, use gsed v3.02 with the "i" flag or sedmod with the -i switch to ignore case on the LHS: @echo off :: sample MS-DOS batch file to alter path statements set old=C:\\SOME\\DOS\\PATH set new=D:\\MY\\NEW\\PATH gsed "s|%old%|%new%|gi" infile >outfile :: or :: sedmod -i "s|%old%|%new%|g" infile >outfile set old= set new= Also, remember that under Win95 long filenames may be stored in two formats: e.g., as "C:\Program Files" or as "C:\PROGRA~1". 4.18. How do I convert files with toggle characters, like +this+, to look like [i]this[/i]? Input files, especially message-oriented text files, often contain toggle characters for emphasis, like ~this~, *this*, or =this=. Sed can make the same input pattern produce alternating output each time it is encountered. Typical needs might be to generate HMTL codes or print codes for boldface, italic, or underscore. This script accomodates multiple occurrences of the toggle pattern on the same line, as well as cases where the pattern starts on one line and finishes several lines later, even at the end of the file: # sed script to convert +this+ to [i]this[/i] :a /+/{ x; # If "+" is found, switch hold and pattern space /^ON/{ # If "ON" is in the (former) hold space, then .. s///; # .. delete it x; # .. switch hold space and pattern space back s|+|[/i]|; # .. turn the next "+" into "[/i]" ba; # .. jump back to label :a and start over } s/^/ON/; # Else, "ON" was not in the hold space; create it x; # Switch hold space and pattern space s|+|[i]|; # Turn the first "+" into "[i]" ba; # Branch to label :a to find another pattern } #---end of script--- This script uses the hold space to create a "flag" to indicate whether the toggle is ON or not. We have added remarks to illustrate the script logic, but in most versions of sed remarks are not permitted after 'b'ranch commands or labels. If you are sure that the +toggle+ characters never cross line boundaries (i.e., never begin on one line and end on another), this script can be reduced to one line: s|+\([^+][^+]*\)+|[i]\1[/i]|g If your toggle pattern contains regex metacharacters (such as * and +, in the case of HHsed), remember to quote them with backslashes. 4.19. How do I delete only the first occurrence of a pattern? To delete only the first line that contains the pattern RE, where "RE" is any regular expression, but leave all other lines containing RE alone, do this: gsed '0,/RE/{//d}' file # GNU sed 3.02.80 sed '/RE/{x;/Y/!{s/^/Y/;h;d;};x;}' file # other seds And if you *know* the pattern will not occur on line 1 and you don't use GNU sed, this will work: sed '1,/RE/{/RE/d;}' file 4.20. How do I commify a string of numbers? Use the simplest script necessary to accomplish your task. As variations of the line increase, the sed script must become more complex to handle additional conditions. Whole numbers are simplest, followed by decimal formats, followed by embedded words. Case 1: simple strings of whole numbers separated by spaces or commas, with an optional negative sign. To convert this: 4381, -1222333, and 70000: - 44555666 1234567890 words 56890 -234567, and 89222 -999777 345888777666 chars to this: 4,381, -1,222,333, and 70,000: - 44,555,666 1,234,567,890 words 56,890 -234,567, and 89,222 -999,777 345,888,777,666 chars use one of these one-liners: sed ':a;s/\B[0-9]\{3\}\>/,&/;ta' # GNU sed sed -e :a -e 's/\(.*[0-9]\)\([0-9]\{3\}\)/\1,\2/;ta' # other seds Case 2: strings of numbers which may have an embedded decimal point, separated by spaces or commas, with an optional negative sign. To change this: 4381, -6555.1212 and 70000, 7.18281828 44906982.071902 56890 -2345.7778 and 8.0000: -49000000 -1234567.89012 to this: 4,381, -6,555.1212 and 70,000, 7.18281828 44,906,982.071902 56,890 -2,345.7778 and 8.0000: -49,000,000 -1,234,567.89012 use the following command for GNU sed: sed ':a;s/\(^\|[^0-9.]\)\([0-9]\+\)\([0-9]\{3\}\)/\1\2,\3/g;ta' and for other versions of sed: sed -f case2.sed files # case2.sed s/^/ /; # add space to start of line :a s/\( [-0-9]\{1,\}\)\([0-9]\{3\}\)/\1,\2/g ta s/ //; # remove space from start of line #---end of script--- ------------------------------ 5. WHY ISN'T THIS WORKING? 5.1. Why don't my variables like $var get expanded in my sed script? Because your sed script uses 'single quotes' instead of "double quotes". Unix shells never expand $variables in single quotes. This is probably the most frequently-asked sed question. For more info on using variables, see section 4.8. 5.2. I'm using 'p' to print, but I have duplicate lines sometimes. Sed prints the entire file by default, so the 'p' command might cause the duplicate lines. If you want the whole file printed, try removing the 'p' from commands like 's/foo/bar/p'. If you want part of the file printed, run your sed script with -n flag to suppress normal output, and rewrite the script to get all output from the 'p' comand. If you're still getting duplicate lines, you are probably finding several matches for the same line. Suppose you want to print lines with the words "Peter" or "James" or "John", but not the same line twice. The following command will fail: sed -n '/Peter/p; /James/p; /John/p' files Since all 3 commands of the script are executed for each line, you'll get extra lines. A better way is to use the 'd' (delete) or 'b' (branch) commands, like so (with GNU sed): sed '/Peter/b; /James/b; /John/b; d' files # one way sed -n '/Peter/{p;d;};/James/{p;d;};/John/p' files # a 2nd way sed -n '/Peter/{p;b;};/James/{p;b;};/John/p' files # a 3rd way sed '/Peter\|James\|John/!d' files # best way :-) On standard seds, these must be broken down with -e commands: sed -e '/Peter/b' -e '/James/b' -e '/John/b' -e d files sed -n -e '/Peter/{p;d;}' -e '/James/{p;d;}' -e '/John/p' files The 3rd line would require too many -e commands to fit on one line, since standard versions of sed require an -e command after each 'b' and also after each closing brace '}'. 5.3. Why does my DOS version of sed process a file part-way through and then quit? First, look for errors in the script. Have you used the -n switch without telling sed to print anything to the console? Have you read the docs to your version of sed to see if it has switches or a syntax you may have misused? If you are sure your sed script is valid, a probable cause is an end-of-file (EOF) marker embedded in the file. An EOF marker (a/k/a SUB) is a Control-Z character, with the values of 1A hex or 026 decimal. As soon as any DOS version of sed encounters a Ctrl-Z character, sed stops processing. To locate the EOF character, use Vern Buerg's shareware file viewer LIST.COM <http://www.buerg.com/list.html>. In text mode, look for a right-arrow symbol; in hex mode (Alt-H), look for a 1A code. With Unix utilities ported to DOS, use 'od' (octal dump) to display hexcodes in your file, and then use sed to locate the offending character: od -txC badfile.txt | sed -n "/ 1a /p; / 1a$/p" Then edit the input file to remove the offending character(s). If you would rather NOT edit the input file, there is still a fix. It requires the DJGPP 32-bit port of 'tr', the Unix translate program, ver 1.22. This version is included as one of the GNU text utilities, available at http://www.simtel.net/pub/simtelnet/gnu/djgpp/v2gnu/txt122b.zip It is important to get the DJGPP version of 'tr' because other versions ported to DOS will stop processing when they encounter the EOF character. Use the -d (delete) command: tr -d \32 < badfile.txt | sed -f myscript.sed 5.4. My RE isn't matching/deleting what I want it to. (Or, "Greedy vs. stingy pattern matching") The two most common causes for this problem are: (1) misusing the '.' metacharacter, and (2) misusing the '*' metacharacter. The RE '.*' is designed to be "greedy" (i.e., matching as many characters as possible). However, sometimes users need an expression which is "stingy," matching the shortest possible string. (1) On single-line patterns, the '.' metacharacter matches any single character on the line. ('.' cannot match the newline at the end of the line because the newline is removed when the line is put into the pattern space; sed adds a newline automatically when the pattern space is printed.) On multi-line patterns obtained with the 'N' or 'G' commands, '.' _will_ match a newline in the middle of the pattern space. If there are 3 lines in the pattern space, "s/.*//" will delete all 3 lines, not just the first one (leaving 1 blank line, since the trailing newline is added to the output). Normal misuse of '.' occurs in trying to match a word or bounded field, and forgetting that '.' will also cross the field limits. Suppose you want to delete the first word in braces: echo {one} {two} {three} | sed 's/{.*}/{}/' # fails echo {one} {two} {three} | sed 's/{[^}]*}/{}/' # succeeds 's/{.*}/{}/' is not the solution, since the regex '.' will match any character, including the close braces. Replace the '.' with '[^}]', which signifies a negated character set '[^...]' containing anything other than a right brace. FWIW, we know that 's/{one}/{}/' would also solve our question, but we're trying to illustrate the use of the negated character set: [^anything-but-this]. A negated character set should be used for matching words between quote marks, for fields separated by commas, etc. See also section 4.5 ("How do I parse a comma-delimited data file?"), above. (2) The '*' metacharacter represents zero or more instances of the previous expression. The '*' metacharacter looks for the leftmost possible match first and will match zero characters. Thus, echo foo | sed 's/o*/EEE/' will generate 'EEEfoo', not 'fEEE' as one might expect. This is because /o*/ matches the null string at the beginning of the word. After finding the leftmost possible match, the '*' is GREEDY; it always tries to match the longest possible string. When two or three instances of '.*' occur in the same RE, the leftmost instance will grab the most characters. Consider this example, which uses grouping '\(...\)' to save patterns: echo bar bat bay bet bit | sed 's/^.*\(b.*\)/\1/' What will be displayed is 'bit', never anything longer, because the leftmost '.*' took the longest possible match. Remember this rule: "leftmost match, longest possible string, zero also matches." 5.5. What is CSDPMI*B.ZIP and why do I need it? If you boot to MS-DOS instead of Windows and try to use GNU sed v1.18 or 3.02, you may encounter the following error message: no DPMI - Get csdpmi*b.zip "DPMI" stands for DOS Protected Mode Interface; it's basically a means of running DOS in Protected Mode (as opposed to Real Mode), which allows programs to share resources in extended memory without conflicting with one another. Running HIMEM.SYS and EMM386.EXE is not enough. The "CSDPMI*B.ZIP" refers to files written by Charles Sandmann to provide DPMI services for 32-bit computers (i.e., 386SX, 386DX, 486SX, etc.). Download this file: http://www.simtel.net/pub/simtelnet/gnu/djgpp/v2misc/csdpmi4b.zip ftp://ftp.cdrom.com/pub/simtelnet/gnu/djgpp/v2misc/csdpmi4b.zip and extract CWSDPMI.EXE, CWSDPR0.EXE and CWSPARAM.EXE from the ZIP file. Put all 3 CWS*.EXE files in the same directory as GSED.EXE and you're all set. There are DOC files enclosed, but they're nearly incomprehensible for the average computer user. (Another case of user-vicious documentation.) If you're running Windows and you normally use a DOS session to run GNU sed (i.e., you get to a DOS prompt with a resizable window or you press Alt-Enter to switch to full-screen mode), you don't need the CWS*.EXE files at all, since Windows uses DPMI already. 5.6. Where are the man pages for GNU sed? Prior to GNU sed v3.02, there weren't any. Until recently, man pages distributed with gsed were borrowed from old sources or from other compilations. None of them were "official." Even the man and info pages distributed with gsed 3.02 are incomplete. For example, they omit special regexes recognized by GNU sed not in most seds; see section 6.8.3 ("Special syntax in REs"), below. 5.7. How do I tell what version of sed I am using? Try entering "sed" all by itself on the command line, followed by no arguments or parameters. Also, try "sed --version". In a pinch, you can also try this: strings sed | grep -i ver Your version of 'strings' must be a version of the Unix utility of this name. It should not be the DOS utility STRINGS.COM by Douglas Boling. 5.8. Does sed issue an exit code? Most versions of sed do not, but check the documentation that came with whichever version you are using. GNU sed issues an exit code of 0 if the program terminated normally, 1 if there were errors in the script, and 2 if there were errors during script execution. 5.9. The 'r' command isn't inserting the file into the text. On most versions of sed (except HHsed and gsed-3.02), the 'r' (read) and 'w' (write) commands must be followed by exactly one space, then the filename, and then terminated by a newline. Any additional characters before or after the filename are interpreted as being part of the filename. Thus "/RE/r insert.me" would try to locate a file called ' insert.me' (note the leading space!). If the file was not found, sed says nothing -- not even an error message. When sed scripts are used on the command line, every 'r' and 'w' must be the last command in that part of the script. Thus, sed -e '/regex/{r insert.file;d;}' source # will fail | sed -e '/regex/{r insert.file' -e 'd;}' source # will succeed | 5.10. Why can't I match or delete a newline using the \n escape | sequence? Why can't I match 2 or more lines using \n? | The \n will never match the newline at the end-of-line because the | newline is always stripped off before the line is placed into the | pattern space. To get 2 or more lines into the pattern space, use | the 'N' command or something similar (such as 'H;...;g;'). | Sed works like this: sed reads one line at a time, chops off the | terminating newline, puts what is left into the pattern space where | the sed script can address or change it, and when the pattern space | is printed, appends a newline to stdout (or to a file). If the | pattern space is entirely or partially deleted with 'd' or 'D', the | newline is *not* added in such cases. Thus, scripts like | sed 's/\n//' file # to delete newlines from each line | sed 's/\n/foo\n/' file # to add a word to the end of each line | will NEVER work, because the trailing newline is removed _before_ | the line is put into the pattern space. To perform the above tasks, | use one of these scripts instead: | tr -d '\n' < file # use tr to delete newlines | sed ':a;N;$!ba;s/\n//g' file # GNU sed to delete newlines | sed 's/$/ foo/' file # add "foo" to end of each line | Since versions of sed other than GNU sed have limits to the size of | the pattern buffer, the Unix 'tr' utility is to be preferred here. | If the last line of the file contains a newline, GNU sed will add | that newline to the output but delete all others, whereas tr will | delete all newlines. | To match a block of two or more lines, there are 3 basic choices: | (1) use the 'N' command to add the Next line to the pattern space; | (2) use the 'H' command at least twice to append the current line | to the Hold space, and then retrieve the lines from the hold space | with x, g, or G; or (3) use address ranges (see section 3.3, above) | to match lines between two specified addresses. | Choices (1) and (2) will put an \n into the pattern space, where it | can be addressed as desired ('s/ABC\nXYZ/alphabet/g'). One example | of using 'N' to delete a block of lines appears in section 4.13 | ("How do I delete a block of _specific_ consecutive lines?"). This | example can be modified by changing the delete command to something | else, like 'p' (print), 'i' (insert), 'c' (change), 'a' (append), | or 's' (substitute). | Choice (3) will not put an \n into the pattern space, but it _does_ | match a block of consecutive lines, so it may be that you don't | even need the \n to find what you're looking for. Since GNU sed | version 3.02.80 now supports this syntax: | sed '/start/,+4d' # to delete "start" plus the next 4 lines, | in addition to the traditional '/from here/,/to there/{...}' range | addresses, it may be possible to avoid the use of \n entirely. | 5.11. My script aborts with an error message, "event not found". | This error is generated by the csh or tcsh shells, not by sed. The | exclamation mark (!) is special to csh/tcsh, and if you use it in | command-line or shell scripts--even within single quotes--it must | be preceded by a backslash. Thus, under the csh/tcsh shell: | sed '/regex/!d' # will fail | sed '/regex/\!d' # will succeed | The exclamation mark should not be prefixed with a backslash when | the script is called from a file, as "-f script.file". | ------------------------------ 6. OTHER ISSUES 6.1. I have a certain problem that stumps me. Where can I get help? Newsgroups: - alt.comp.editors.batch (best choice) - comp.editors - comp.unix.questions - comp.unix.shell Send e-mail to: owner-sed-users@jpusa.chi.il.us Your question will be posted on the "sed-users" mailing list, where many sed users will be able to see your question. Sending your question will not automatically subscribe you to the list. 6.2. How does sed compare with awk, perl, and other utilities? Awk is a much richer language with many features of a programming language, including variable names, math functions, arrays, system calls, etc. Its command structure is similar to sed: address { command(s) } which means that for each line or range of lines that matches the address, execute the command(s). In both sed and awk, an address can be a line number or a RE somewhere on the line, or both. In program size, awk is 3-10 times larger than sed. Awk has most of the functions of sed, but not all. Notably, sed supports backreferences (\1, \2, ...) to previous expressions, and awk does not have any comparable function or syntax. Perl is a general-purpose programming language, with many features beyond text processing and interprocess communication, taking it well past awk or other scripting languages. Perl supports every feature sed does and has its own set of extended regular expressions, which give it extensive power in pattern matching and processing. (Note: the standard perl distribution comes with 's2p', a sed-to-perl conversion script. See section 3.6 for more info.) Like sed and awk, perl scripts do not need to be compiled into binary code. Like sed, perl can also run many useful "one-liners" from the command line, though with greater flexibility; see question 4.3 ("How do I make substitutions in every file in a directory, or in a complete directory tree?"). On the other hand, the current version of perl is from 8 to 35 times larger than sed in its executables alone (perl's library modules and allied files not included!). Further, for most simple tasks such as substitution, sed executes more quickly than either perl or awk. All these utilities serve to process input text, transforming it to meet our needs . . . or our arbitrary whims. 6.3. When should I use sed? When you need a small, fast program to modify words, lines, or blocks of lines in a textfile. 6.4. When should I NOT use sed? You should not use sed when you have "dedicated" tools which can do the job faster or with an easier syntax. Do not use sed when you only want to: - delete individual characters. Instead of "s/[abcd]//g", use tr -d "[a-d]" - squeeze sequential characters. Instead of "s/ee*/e/g", use tr -s "{character-set}" - change individual characters. Instead of "y/abcdef/ABCDEF/", use tr "[a-f]" "[A-F]" - print individual lines, based on patterns within the line itself. Instead, use "grep". - print blocks of lines, with 1 or more lines of context above and/or below a specific regular expression. Instead, use the GNU version of grep as follows: grep -A{number} -B{number} - remove individual lines, based on patterns within the line itself. Instead, use "grep -v". - print line numbers. Instead, use "nl" or "cat -n". - reformat lines or paragraphs. Instead, use "fold", "fmt" or "par". Though sed can perfectly emulate certain functions of cat, grep, nl, rev, sort, tac, tail, tr, uniq, and other utilities, producing identical output, the native utilities are usually optimized to do the job more quickly than sed. 6.5. When should I ignore sed and use Awk or Perl instead? If you can write the same script in Awk or Perl and do it in less time, then use Perl or Awk. There's no reason to spend an hour writing and debugging a sed script if you can do it in Perl in 10 minutes (assuming that you know Perl already) and if the processing time or memory use is not a factor. Don't hunt pheasants with a .22 if you have a shotgun at your side . . . unless you simply enjoy the challenge! Specifically, if you need to: - heavily comment what your scripts do. Use GNU sed, awk, or perl. - do case insensitive searching. Use gsed302, sedmod, awk or perl. - count fields (words) in a line. Use awk. - count lines in a block or objects in a file. Use awk. - check lengths of strings or do math operations. Use awk or perl. - handle very long lines or need very large buffers. Use gsed or perl. - handle binary data (control characters). Use perl (binmode). - loop through an array or list. Use awk or perl. - test for file existence, filesize, or fileage. Use perl or shell. - treat each paragraph as a line. Use awk or perl. - indicate /alternate|options/ in regexes. Use gsed, awk or perl. - use syntax like \xNN to match hex codes. Use gsed-3.02.80 or perl. - use (nested (regexes)) with backreferences. Use perl. Perl lovers: I know that perl can do everything awk can do, but please don't write me to complain. Why heft a shotgun when a .45 will do? As we all know, "There is more than one way to do it." 6.6. Known limitations among sed versions Limits on distributed versions, although source code for most versions of free sed allows for modification and recompilation. The term "no limit" when used below means there is no "fixed" limit. Limits are actually determined by one's hardware, memory, operating system, and which C library is used to compile sed. 6.6.1. Maximum line length GNU sed 3.02: no limit GNU sed 2.05: no limit sedmod 1.0: 4096 bytes HHsed: 4000 bytes 6.6.2. Maximum size for all buffers (pattern space + hold space) GNU sed 3.02: no limit GNU sed 2.05: no limit sedmod 1.0: 4096 bytes HHsed: 4000 bytes 6.6.3. Maximum number of files that can be read with read command GNU sed 3.02: no limit GNU sed 2.05: total no. of r and w commands may not exceed 32 sedmod 1.0: total no. of r and w commands may not exceed 20 6.6.4. Maximum number of files that can be written with 'w' command GNU sed 3.02: no limit (but typical Unix is 253) GNU sed 2.05: total no. of r and w commands may not exceed 32 sedmod 1.0: 10 HHsed: 10 6.6.5. Limits on length of label names BSD sed: 8 characters GNU sed 3.02: no limit GNU sed 2.05: no limit HHsed: no limit 6.6.6. Limits on length of write-file names BSD sed: 40 characters GNU sed 3.02: no limit GNU sed 2.05: no limit HHsed: no limit 6.6.7. Limits on branch/jump commands HHsed: 50 As a practical consequence, this means that HHsed will not read more than 50 lines into the pattern space via an N command, even if the pattern space is only a few hundred bytes in size. HHsed exits with an error message, "infinite branch loop at line {nn}". 6.7. Known bugs among sed versions A. GNU sed v3.02.80 (1) N does not discard the contents of the pattern space upon | reaching the end of file; not a bug. See section 6.8.6, below. | B. GNU sed v3.02 (1) Affects only v3.02 binaries compiled with DJGPP for MS-DOS and MS-Windows: 'l' (list) command does not display a lone carriage return (0x0D, ^M) embedded in a line. (2) The expression "\<" causes problems when attempting the following types of substitutions, which should print "+aaa +bbb": echo aaa bbb | sed 's/\</+/g' # prints "+a+a+a +b+b+b" echo aaa bbb | sed 's/\<./+&/g' # prints "+a+a+a +b+b+b" (3) The N command no longer discards the contents of the pattern | space upon reaching the end of file. This is not a bug, it's a | feature. See section 6.8.6 "Commands which operate differently". | C. GNU sed v2.05 (1) If a number follows the substitute command (e.g., s/f/F/10) and the number exceeds the possible matches on the pattern space, the command 't label' _always_ jumps to the specified label. 't' should jump only if the substitution was successful (or returned "true"). (2) 'l' (list) command does not convert the following characters to hex values, but passes them through unchanged: 0xF7, 0xFB, 0xFC, 0xFD, 0xFE. (3) A range address like "/foo/,14d" should delete every line from the first occurrence of "foo" until line 14, inclusive, and then if /foo/ occurs thereafter, delete only those lines. In gsed 2.05, if a second "foo" occurs in the file, that line and everything to the end of file will be deleted (since gsed is looking for line 14 to occur again!). (4) The regex /\'/ is not interpreted as an apostrophe or a single quote mark, as it should be. Instead, it is interpreted as $, representing the end-of-line! This can be proven by these tests: echo hello | gsed "/\'/d" # entire line is deleted! echo hello | gsed "s/\'/YYY/" # 'YYY' appended to string (5) Multiple occurrences of the 'w' command fail, as shown here, given that both "aaa" and "bbb" occur within the file: gsed -e "/aaa/w FILE" -e "/bbb/w FILE" input.txt (6) The expression "\<" causes problems when attempting the following type of substitution, which should print "+aaa +bbb": echo aaa bbb | sed 's/\</+/g' # sed hangs up with no output The syntax 's/\<./+&/g' issues the proper output. D. GNU sed v1.18 (1) same as #1 for GNU sed v2.05, above. (2) The following command will lock the computer under Win95. Echos is an echo command that does not issue a trailing newline: echos any_word | gsed "s/[ ]*$//" (3) same as #3 for GNU sed v2.05, above. E. GNU sed v1.03 (by Frank Whaley) (1) The \w and \W escape sequences both match only nonword characters. \w is misdefined and should match word characters. (2) The underscore is defined as a nonword character; it should be defined as a word character. (3) same as #3 for GNU sed v2.05, above. F. HHsed v1.5 (by Howard Helman) (1) If a number follows the substitute command (e.g., s/foo/bar/2), in a sed script entered from the command line, two semicolons must follow the number, or they must be separated by an -e switch. Normally, only 1 semicolon is needed to separate commands. echo bit bet | HHsed "s/b/n/2;;s/b/B/" # solution 1 echo bit bet | HHsed -e "s/b/n/2" -e "s/b/B" # solution 2 (2) If the substitute command is followed by a number and a "p" flag, when the -n switch is used, the "p" flag must occur first. echo aaa | HHsed -n "s/./B/3p" # bug! nothing prints echo aaa | HHsed -n "s/./B/p3" # prints "aaB" as expected (3) The following commands will cause HHsed to lock the computer under MS-DOS or Win95. Note that they occur because of malformed regular expressions which will match no characters. sed -n "p;s/\<//g;" file sed -n "p;s/[char-set]*//g;" file (4) The range command '/RE1/,/RE2/' in HHsed will match one line if both regexes occur on the same line (see section 6.8.5, below). Though this could be construed as a feature, it should probably be considered a bug since its operation differs from every other version of sed. For example, '/----/,/----/{s/^/>>/;}' should put two angle brackets ">>" before every line which is sandwiched between a row of 4 or more hyphens. With HHsed, this command will only prefix the hyphens themselves with the angle brackets. (5) If the hold space is empty, the H command copies the pattern space to the hold space but fails to prepend a leading newline. The H command is supposed to add a newline, followed by the contents of the pattern space, to the hold space at all times. A workaround is "{G;s/^\(.*\)\(\n\)$/\2\1/;H;s/\n$//;}", but it requires knowing that the hold space is empty and using the command only once. Another alternative is to use the G or the A command alone at key points in the script. (6) If grouping is followed by an '*' or '+' operator, HHsed does not match the pattern, but issues no warning. See below: echo aaa | HHsed "/\(a\)*/d" # nothing is deleted echo aaa | HHsed "/\(a\)+/d" # nothing is deleted echo aaa | HHsed "s/\(a\)*/\1B/" # nothing is changed echo aaa | HHsed "s/\(a\)+/\1B/" # nothing is changed (7) If grouping is followed by an interval expression, HHsed halts with the error message "garbled command", in all of the following examples: echo aaa | HHsed "/\(a\)\{3\}/d" echo aaa | HHsed "/\(a\)\{1,5\}/d" echo aaa | HHsed "s/\(a\)\{3\}/\1B/" (8) In interval expressions, 0 is not supported. E.g., \{0,3\) G. sedmod v1.0 (by Hern Chen) Technically, the following are limits (or features?) of sedmod, not bugs, since the docs for sedmod do not claim to support these missing features. (1) sedmod does not support standard range arguments \{...\} present in nearly all versions of sed. (2) If grouping is followed by an '*' or '+' operator, sedmod gives a "garbled command" message. However, if the grouped expressions are strings literals with no metacharacters, a partial workaround can be done like so: \(string\)\1* # matches 1 or more instances of 'string' \(string\)\1+ # matches 2 or more instances of 'string' (3) sedmod does not support a numeric argument after the s/// command, as in 's/a/b/3', present in nearly all versions of sed. The following are bugs in sedmod v1.0: (4) When the -i (ignore case) switch is used, the '/regex/d' command is not properly obeyed. Sedmod may miss one or more lines matching the expression, regardless of where they occur in the script. Workaround: use "/regex/{d;}" instead. H. HP-UX sed (1) Versions of HP-UX sed up to and including version 10.20 are buggy. According to the README file, which comes with the GNU cc at <ftp://ftp.ntua.gr/pub/gnu/sed-2.05.bin.README>: "When building gcc on a hppa*-*-hpux10 platform, the `fixincludes' step (which involves running a sed script) fails because of a bug in the vendor's implementation of sed. Currently the only known workaround is to install GNU sed before building gcc. The file sed-2.05.bin.hpux10 is a precompiled binary for that platform." I. SunOS 4.1 sed (1) Bug occurs in RE pattern matching when a non-null '[char-set]*' is followed by a null '\NUM' pattern recall, illustrated here and reported by Greg Ubben: s/\(a\)\(b*\)cd\1[0-9]*\2foo/bar/ # between '[0-9]*' and '\2' s/\(a\{0,1\}\).\{0,1\}\1/bar/ # between '.\{0,1\}' and '\1' Workaround: add a do-nothing 'X*' expression which will not match any characters on the line between the two components. E.g., s/\(a\)\(b*\)cd\1[0-9]*X*\2foo/bar/ s/\(a\{0,1\}\).\{0,1\}X*\1/bar/ J. SunOS 5.6 sed (1) If grouping is followed by an asterisk, SunOS sed does not match the null string, which it should do. The following command: echo foo | sed 's/f\(NO-MATCH\)*/g\1/' should transform "foo" to "goo" under normal versions of sed. K. Ultrix 4.3 sed (1) If grouping is followed by an asterisk, Ultrix sed replies with "command garbled", as shown in the following example: echo foo | sed 's/f\(NO-MATCH\)*/g\1/' (2) If grouping is followed by a numeric operator such as \{0,9\}, Ultrix sed does not find the match. L. Digital Unix sed (1) The following comes from the man pages for sed distributed with new, 1998 versions of Digital Unix (reformatted to fit our margins): [Digital] The h subcommand for sed does not work properly. When you use the h subcommand to place text into the hold area, only the last line of the specified text is saved. You can use the H subcommand to append text to the hold area. The H subcommand and all others dealing with the hold area work correctly. (2) "$d" command issues an error message, "cannot parse". Reported by Carlos Duarte on 8 June 1998. 6.8. Known incompatibilities between sed versions 6.8.1. Issuing commands from the command line Most versions of sed permit multiple commands to issued on the command line, separated by a semicolon (;). Thus, sed 'G;G' file should triple-space a file. However, certain commands REQUIRE separate expressions on the command line. These include: - all labels (':a', ':more', etc.) - all branching instructions ('b', 't') - commands to read and write files ('r' and 'w') - any closing brace, '}' If these commands are used, they must be the LAST commands of an expression. Subsequent commands must use another expression (another -e switch plus arguments). E.g., sed -e :a -e 's/^.\{1,77\}$/ &/;ta' -e 's/\( *\)\1/\1/' files GNU sed and HHsed v1.5 allow these commands to be followed by a semicolon, and the previous script can be written like this: sed ':a;s/^.\{1,77\}$/ &/;ta;s/\( *\)\1/\1/' files Versions differ in implementing the 'a' (append), 'c' (change), and 'i' (insert) commands: sed "/foo/i New text here" # HHsed/sedmod/gsed-30280 gsed -e "/foo/i\\" -e "New text here" # GNU sed sed1 -e "/foo/i" -e "New text here" # one version of sed sed2 "/foo/i\ New text here" # another version 6.8.2. Using comments (prefixed by the '#' sign) Most versions of sed permit comments to appear in sed scripts only on the first line of the script. Comments on line 2 or thereafter are not recognized and will generate an error like "unrecognized command" or "command [bad-line-here] has trailing garbage". GNU sed, HHsed, sedmod, and HP-UX sed permit comments to appear on any line of the script, except after labels and branching commands (b,t), *provided* that a semicolon (;) occurs after the command itself. This syntax makes sed similar to awk and perl, which use a similar commenting structure in their scripts. Thus, # GNU style sed script $!N; # except for last line, get next line s/^\([0-9]\{5\}\).*\n\1.*//; # if first 5 digits of each line # match, delete BOTH lines. t skip P; # print 1st line only if no match :skip D; # delete 1st line of pattern space and loop #---end of script--- is a valid script for GNU sed and Helman's sed, but is unrecognized for most other versions of sed. 6.8.3. Special syntax in REs A. GNU sed v2.05 and higher versions BEGIN~STEP selection: GNU sed can select a series of lines in the form M~N, where M and N are integers (with gsed v2.05, M must be less than N). Beginning at line M (M may equal 0), every Nth line is selected. Thus, gsed '1~3d' file # delete every 3d line, starting with line 1 # deletes lines 1, 4, 7, 10, 13, 16, ... gsed -n '2~5p' file # print every 5th line, starting with line 2 # prints lines 2, 7, 12, 17, 22, 27, ... With gsed v3.02, M may be any valid line number. With gsed v2.05, if M is greater than or equal to N (the STEP value), nothing will be selected, except in one pointless case, 0~0, which selects every line. The following expressions can be used for /RE/ addresses or in the LHS side of a substitution: \` - matches the beginning of the pattern space (same as "^") \' - matches the end of the pattern space (same as "$") \? - 0 or 1 occurrences of previous character: same as \{0,1\} \+ - 1 or more occurrences of previous character: same as \{1,\} \| - matches the string on either side, e.g., foo\|bar \b - boundary between word and nonword chars (reversible) \B - boundary between 2 word or between 2 nonword chars \n - embedded newline (usable after N, G, or similar commands) \w - any word character: [A-Za-z0-9_] \W - any nonword char: [^A-Za-z0-9_] \< - boundary between nonword and word character \> - boundary between word and nonword character On \b, \B, \<, and \>, see section 6.8.4 ("Word boundaries"), below. Beginning with version 3.02.80, the following escape sequences can now be used on both sides of a "s///" substitution: \a "alert" beep (BEL, Ctrl-G, 0x07) \f formfeed (FF, Ctrl-L, 0x0C) \n newline (LF, Ctrl-J, 0x0A) \r carriage-return (CR, Ctrl-M, 0x0D) \t horizontal tab (HT, Ctrl-I, 0x09) \v vertical tab (VT, Ctrl-K, 0x0B) \oNNN a character with the octal value NNN \dNNN a character with the decimal value NNN \xNN a character with the hexadecimal value NN Note that gsed does not have any syntax for designating characters in octal or hex notation. Traditionally, \ooo or \hh or \xhh have been used by the GNU project to do this, but they are not (yet) implemented in gsed. Note that GNU sed also supports "character classes", a POSIX extension to regexes, described in section 3.7, above. B. GNU sed v1.03 (by Frank Whaley) When used with the -x (extended) switch on the command line, or when '#x' occurs as the first line of a script, Whaley's gsed103 supports the following expressions in both the LHS and RHS of a substitution: \| matches the expression on either side ? 0 or 1 occurrences of previous RE: same as \{0,1\} + 1 or more occurrence of previous RE: same as \{1,\} \a "alert" beep (BEL, Ctrl-G, 0x07) \b backspace (BS, Ctrl-H, 0x08) \f formfeed (FF, Ctrl-L, 0x0C) \n newline (LF, Ctrl-J, 0x0A) \r carriage-return (CR, Ctrl-M, 0x0D) \t horizontal tab (HT, Ctrl-I, 0x09) \v vertical tab (VT, Ctrl-K, 0x0B) \bBBB binary char, where BBB are 1-8 binary digits, [0-1] \dDDD decimal char, where DDD are 1-3 decimal digits, [0-9] \oOOO octal char, where OOO are 1-3 octal digits, [0-7] \xXX hex char, where XX are 1-2 hex digits, [0-9A-F] In normal mode, with or without the -x switch, the following escape sequences are also supported in regex addressing or in the LHS of a substitution: \` matches beginning of pattern space: same as /^/ \' matches end of pattern space: same as /$/ \B boundary between 2 word or 2 nonword characters \w any nonword character [*BUG!* should be a word char] \W any nonword character: same as /[^A-Za-z0-9]/ \< boundary between nonword and word char \> boundary between word and nonword char C. HHsed v1.5 (by Howard Helman) The following expressions can be used for /RE/ addresses or in the LHS and RHS side of a substitution: + - 1 or more occurrences of previous RE: same as \{1,\} \a - bell (ASCII 07, 0x07) \b - backspace (ASCII 08, 0x08) \e - escape (ASCII 27, 0x1B) \f - formfeed (ASCII 12, 0x0C) \n - newline (printed as 2 bytes, 0D 0A or ^M^J, in DOS) \r - return (ASCII 13, 0x0D) \t - tab (ASCII 09, 0x09) \v - vertical tab (ASCII 11, 0x0B) \xhh - the ASCII character corresponding to 2 hex digits hh. \< - boundary between nonword and word character \> - boundary between word and nonword character D. sedmod v1.0 (by Hern Chen) The following expressions can be used for /RE/ addresses in the LHS of a substitution: + - 1 or more occurrences of previous RE: same as \{1,\} \a - any alphanumeric: same as [a-zA-Z0-9] \A - 1 or more alphas: same as \a+ \d - any digit: same as [0-9] \D - 1 or more digits: same as \d+ \h - any hex digit: same as [0-9a-fA-F] \H - 1 or more hexdigits: same as \h+ \l - any letter: same as [A-Za-z] \L - 1 or more letters: same as \l+ \n - newline (read as 2 bytes, 0D 0A or ^M^J, in DOS) \s - any whitespace character: space, tab, or vertical tab \S - 1 or more whitespace chars: same as \s+ \t - tab (ASCII 09, 0x09) \< - boundary between nonword and word character \> - boundary between word and nonword character The following expressions can be used in the RHS of a substitution. "Elements" refer to \1 .. \9, &, $0, or $1 .. $9: & - insert regexp defined on LHS \e - end case conversion of next element \E - end case conversion of remaining elements \l - change next element to lower case \L - change remaining elements to lower case \n - newline (printed as 2 bytes, 0D 0A or ^M^J, in DOS) \t - tab (ASCII 09, 0x09) \u - change next element to upper case \U - change remaining elements to upper case $0 - insert pattern space BEFORE the substitution $1-$9 - match Nth word on the pattern space E. UnixDos sed The following expressions can be used in text, LHS, and RHS: \n - newline (printed as 2 bytes, 0D 0A or ^M^J, in DOS) 6.8.4. Word boundaries GNU sed, HHsed, and sedmod use certain symbols to define the boundary between a "word character" and a nonword character. A word character fits the regex "[A-Za-z0-9_]". Note: a word character includes the underscore "_" but not the hyphen, probably because the underscore is permissible as a label in sed and in other scripting languages. (In gsed103, a word character did NOT include the underscore; it included alphanumerics only.) These symbols include '\<' and '\>' (gsed, HHsed, sedmod) and '\b' and '\B' (gsed only). Note that the boundary symbols do not represent a character, but a position on the line. Word boundaries are used with literal characters or character sets to let you match (and delete or alter) whole words without affecting the spaces or punctuation marks outside of those words. They can only be used in a "/pattern/" address or in the LHS of a 's/LHS/RHS/' command. The following table shows how these symbols may be used in HHsed and GNU sed. Sedmod matches the syntax of HHsed. Match position Possible word boundaries HHsed GNU sed --------------------------------------------------------------- start of word [nonword char]^[word char] \< \< or \b end of word [word char]^[nonword char] \> \> or \b middle of word [word char]^[word char] none \B outside of word [nonword char]^[nonword char] none \B --------------------------------------------------------------- 6.8.5. Range addressing with GNU sed and HHsed When addressing a range of lines, as in the following example to delete all lines between /RE1/ and /RE2/, sed '/RE1/,/RE2/d' file if /RE1/ and /RE2/ both occur on the *same* line, HHsed will delete that single line and then look forward in the file for the next occurrence of /RE1/ to attempt the deletion. GNU sed will match the first line containing /RE1/ but will look forward to the next and succeeding lines to match /RE2/. If /RE1/ and /RE2/ cannot be found on two different lines, nothing will be deleted. GNU sed v2.05 has a bug in range addressing (see section 6.7.C(3), above). This was fixed in gsed v3.02. GNU sed v3.02.80 supports 0 in range addressing, which means that the range "0,/RE/" will match every line from the top of the file to the first line containing /RE/, inclusive, and if /RE/ occurs on the first line of the file, only line 1 will be matched. 6.8.6. Commands which operate differently | A. GNU sed version 3.02 and 3.02.80 | The N command no longer discards the contents of the pattern space | upon reaching the end of file. This is not a bug, it's a feature. | However, it breaks certain scripts which relied on the older | behavior of N. | 'N' adds the Next line to the pattern space, enabling multiple | lines to be stored and acted upon. Upon reaching the last line of | the file, if the N command was issued again, the contents of the | pattern space would be silently deleted and the script would abort | (this has been the traditional behavior). For this reason, sed | users generally wrote: | $!N; # to add the Next line to every line but the last one. | However, certain sed scripts relied on this behavior, such as the | script to delete trailing blank lines at the end of a file (see | script #12 in section 3.2, "Common one-line sed scripts", above). | Also, classic textbooks such as Dale Dougherty and Arnold Robbins' | _sed & awk_ documented the older behavior. | The GNU sed maintainer felt that despite the portability problems | this would cause, changing the N command to print (rather than | delete) the pattern space was more consistent with one's intuitions | about how a command to "append the Next line" _ought_ to behave. | Another fact favoring the change was that "{N;command;}" will | delete the last line if the file has an odd number of lines, but | print the last line if the file has an even number of lines. | To convert scripts which used the former behavior of N (deleting | the pattern space upon reaching the EOF) to scripts compatible with | all versions of sed, change a lone "N;" to "$d;N;". | [end-of-file]