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Archive-Name: editor-faq/sed
Posting-Frequency: irregular
Last-modified: 10 March 2003
Version: 015
Maintainer: Eric Pement (


Frequently Asked Questions about

sed, the stream editor



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


2.1. What is sed?

2.2. What versions of sed are there, and where can I get them?

2.2.1. Free versions Unix platforms OS/2 Microsoft Windows (Win3x, Win9x, WinNT, Win2K) MS-DOS CP/M Macintosh v8 or v9

2.2.2. Shareware and Commercial versions Unix platforms OS/2 Windows 95/98, Windows NT, Windows 2000 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


3.1. More detailed explanation of basic sed

3.1.1. Regular expressions on the left side of "s///"

3.1.2. Escape characters on the right side of "s///"

3.1.3. Substitution switches

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. Address ranges in GNU sed and HHsed

3.5. Debugging sed scripts

3.6. Notes about s2p, the sed-to-perl translator

3.7. GNU/POSIX extensions to regular expressions



4.1. How do I insert a newline into the RHS of a substitution?

4.2. How do I represent control-codes or non-printable characters?

4.3. How do I convert files with toggle characters, like +this+, to look like [i]this[/i]?


4.10. How do I perform a case-insensitive search?

4.11. How do I match only the first occurrence of a pattern?

4.12. How do I parse a comma-delimited (CSV) data file?

4.13. How do I handle fixed-length, columnar data?

4.14. How do I commify a string of numbers?

4.15. How do I prevent regex expansion on substitutions?

4.16. How do I convert a string to all lowercase or capital letters?

CHANGING BLOCKS (consecutive lines)

4.20. How do I change only one section of a file?

4.21. How do I delete or change a block of text if the block contains a certain regular expression?

4.22. How do I locate a paragraph of text if the paragraph contains a certain regular expression?

4.23. How do I match a block of specific consecutive lines?

4.23.1. Try to use a "/range/, /expression/"

4.23.2. Try to use a "multi-line\nexpression"

4.23.3. Try to use a block of "literal strings"

4.24. How do I address all the lines between RE1 and RE2, excluding the lines themselves?

4.25. How do I join two lines if line #1 ends in a [certain string]?

4.26. How do I join two lines if line #2 begins in a [certain string]?

4.27. How do I change all paragraphs to long lines?


4.30. How do I read environment variables with sed ...

4.31.1. ... on Unix platforms?

4.31.2. ... on MS-DOS or 4DOS platforms?

4.32. How do I export or pass variables back into the environment ...

4.32.1. ... on Unix platforms?

4.32.2. ... on MS-DOS or 4DOS platforms?

4.33. How do I handle shell quoting in sed?


4.40. How do I read (insert/add) a file at the top of a textfile?

4.41. How do I make substitutions in every file in a directory, or in a complete directory tree?

4.41.1. ... ssed solution

4.41.2. ... Unix solution

4.41.3. ... DOS solution

4.42. How do I replace "/some/UNIX/path" in a substitution?

4.43. How do I replace "C:\SOME\DOS\PATH" in a substitution?

4.44. How do I emulate file-includes, using sed?


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".


6.1. 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 incompatibilities between sed versions

6.7.1. Issuing commands from the command line

6.7.2. Using comments (prefixed by the '#' sign)

6.7.3. Special syntax in REs

6.7.4. Word boundaries

6.7.5. Commands which operate differently


7.1. ssed v3.59

7.2. GNU sed v4.0 - v4.0.5

7.3. GNU sed v3.02.80

7.4. GNU sed v3.02

7.5. GNU sed v2.05

7.6. GNU sed v1.18

7.7. GNU sed v1.03

7.8. sed v1.6 (Briscoe)

7.9. sed v1.5 (Helman)

7.10. sedmod v1.0 (Chen)

7.11. HP-UX sed

7.12. SunOS sed v4.1

7.13. SunOS sed v5.6

7.14. Ultrix sed v4.3

7.15. Digital Unix sed


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