HANDY ONE-LINERS FOR SED (Unix stream editor)


 # double space a file
 sed G

 # triple space a file
 sed 'G;G'

 # undo double-spacing (assumes even-numbered lines are always blank)
 sed 'n;d'


 # number each line of a file (simple left alignment). Using a tab (see
 # note on '\t' at end of file) instead of space will preserve margins.
 sed = filename | sed 'N;s/\n/\t/'

 # number each line of a file (number on left, right-aligned)
 sed = filename | sed 'N; s/^/     /; s/ *\(.\{6,\}\)\n/\1  /'

 # number each line of file, but only print numbers if line is not blank
 sed '/./=' filename | sed '/./N; s/\n/ /'

 # count lines (emulates "wc -l")
 sed -n '$='


 # IN UNIX ENVIRONMENT: convert DOS newlines (CR/LF) to Unix format
 sed 's/.$//'               # assumes that all lines end with CR/LF
 sed 's/^M$//'              # in bash/tcsh, press Ctrl-V then Ctrl-M
 sed 's/\x0D$//'            # sed v1.5 only

 # IN DOS ENVIRONMENT: convert Unix newlines (LF) to DOS format
 sed 's/$//'                          # method 1
 sed -n p                             # method 2

 # delete leading whitespace (spaces, tabs) from front of each line
 # aligns all text flush left
 sed 's/^[ \t]*//'                    # see note on '\t' at end of file

 # delete trailing whitespace (spaces, tabs) from end of each line
 sed 's/[ \t]*$//'                    # see note on '\t' at end of file

 # delete BOTH leading and trailing whitespace from each line
 sed 's/^[ \t]*//;s/[ \t]*$//'

 # insert 5 blank spaces at beginning of each line (make page offset)
 sed 's/^/     /'

 # align all text flush right on a 79-column width
 sed -e :a -e 's/^.\{1,78\}$/ &/;ta'  # set at 78 plus 1 space

 # center all text in the middle of 79-column width. In method 1,
 # spaces at the beginning of the line are significant, and trailing
 # spaces are appended at the end of the line. In method 2, spaces at
 # the beginning of the line are discarded in centering the line, and
 # no trailing spaces appear at the end of lines.
 sed  -e :a -e 's/^.\{1,77\}$/ & /;ta'                     # method 1
 sed  -e :a -e 's/^.\{1,77\}$/ &/;ta' -e 's/\( *\)\1/\1/'  # method 2

 # substitute (find & replace) "foo" with "bar" on each line
 sed 's/foo/bar/'             # replaces only 1st instance in a line
 sed 's/foo/bar/4'            # replaces only 4th instance in a line
 sed 's/foo/bar/g'            # replaces ALL instances in a line

 # substitute "foo" with "bar" ONLY for lines which contain "baz"
 sed '/baz/s/foo/bar/g'

 # substitute "foo" with "bar" EXCEPT for lines which contain "baz"
 sed '/baz/!s/foo/bar/g'

 # reverse order of lines (emulates "tac")
 sed '1!G;h;$!d'

 # reverse each character on the line (emulates "rev")
 sed '/\n/!G;s/\(.\)\(.*\n\)/&\2\1/;//D;s/.//'

 # join pairs of lines side-by-side (like "paste")
 sed 'N;s/\n/ /'


 # print first 10 lines of file (emulates behavior of "head")
 sed 10q

 # print first line of file (emulates "head -1")
 sed q

 # print last 10 lines of file (emulates "tail")
 sed -e :a -e '$q;N;11,$D;ba'

 # print last line of file (emulates "tail -1")
 sed '$!d'

 # print only lines which match regular expression (emulates "grep")
 sed -n '/regexp/p'           # method 1
 sed '/regexp/!d'             # method 2

 # print only lines which do NOT match regexp (emulates "grep -v")
 sed -n '/regexp/!p'          # method 1, corresponds to above
 sed '/regexp/d'              # method 2, simpler syntax

 # print 1 line of context before and after regexp, with line number
 # indicating where the regexp occurred (similar to "grep -A1 -B1")
 sed -n -e '/regexp/{=;x;1!p;g;$!N;p;D;}' -e h

 # grep for AAA and BBB and CCC (in any order)
 sed '/AAA/!d; /BBB/!d; /CCC/!d'

 # grep for AAA and BBB and CCC (in that order)
 sed '/AAA.*BBB.*CCC/!d'

 # grep for AAA or BBB or CCC (emulates "egrep")
 sed -e '/AAA/b' -e '/BBB/b' -e '/CCC/b' -e d

 # print paragraph if it contains AAA (blank lines separate paragraphs)
 # HHsed v1.5 must insert a 'G;' after 'x;' in the next 3 scripts below
 sed -e '/./{H;$!d;}' -e 'x;/AAA/!d;'

 # print paragraph if it contains AAA and BBB and CCC (in any order)
 sed -e '/./{H;$!d;}' -e 'x;/AAA/!d;/BBB/!d;/CCC/!d'

 # print paragraph if it contains AAA or BBB or CCC
 sed -e '/./{H;$!d;}' -e 'x;/AAA/b' -e '/BBB/b' -e '/CCC/b' -e d

 # print only lines of 65 characters or longer
 sed -n '/^.\{65\}/p'

 # print only lines of less than 65 characters
 sed -n '/^.\{65\}/!p'        # method 1, corresponds to above
 sed '/^.\{65\}/d'            # method 2, simpler syntax

 # print section of file from regular expression to end of file
 sed -n '/regexp/,$p'

 # print section of file based on line numbers (lines 8-12, inclusive)
 sed -n '8,12p'               # method 1
 sed '8,12!d'                 # method 2

 # print line number 52
 sed -n '52p'                 # method 1
 sed '52!d'                   # method 2
 sed '52q;d'                  # method 3, efficient on large files

 # print section of file between two regular expressions (inclusive)
 sed -n '/Iowa/,/Montana/p'             # case sensitive


 # print all of file EXCEPT section between 2 regular expressions
 sed '/Iowa/,/Montana/d'

 # delete duplicate lines from a sorted file (emulates "uniq"). First
 # line in a set of duplicate lines is kept, the rest are deleted
 sed '$!N; /^\(.*\)\n\1$/!P; D'

 # delete ALL blank lines from a file (same as "grep '.' ")
 sed '/^$/d'

 # delete all CONSECUTIVE blank lines from file except the first; also
 # deletes all blank lines from top and end of file (emulates "cat -s")
 sed '/./,/^$/!d'          # method 1, allows 0 blanks at top, 1 at EOF
 sed '/^$/N;/\n$/D'        # method 2, allows 1 blank at top, 0 at EOF

 # delete all CONSECUTIVE blank lines from file except the first 2:
 sed '/^$/N;/\n$/N;//D'

 # delete all leading blank lines at top of file
 sed '/./,$!d'

 # delete all trailing blank lines at end of file
 sed -e :a -e '/^\n*$/N;/\n$/ba'

 # delete the last line of each paragraph
 sed -n '/^$/{p;h;};/./{x;/./p;}'


 # remove nroff overstrikes (char, backspace) from man pages. The 'echo'
 # command may need an -e switch if you use Unix System V or bash shell.
 sed "s/.`echo \\\b`//g"    # double quotes required for Unix environment
 sed 's/.^H//g'             # in bash/tcsh, press Ctrl-V and then Ctrl-H
 sed 's/.\x08//g'           # hex expression for sed v1.5

 # get Usenet/e-mail message header
 sed '/^$/q'                # deletes everything after first blank line

 # get Usenet/e-mail message body
 sed '1,/^$/d'              # deletes everything up to first blank line

 # get Subject header, but remove initial "Subject: " portion
 sed '/^Subject: */!d; s///;q'

 # get return address header
 sed '/^Reply-To:/q; /^From:/h; /./d;g;q'

 # parse out the address proper. Pulls out the e-mail address by itself
 # from the 1-line return address header (see preceding script)
 sed 's/ *(.*)//; s/>.*//; s/.*[:<] *//'

 # add a leading angle bracket and space to each line (quote a message)
 sed 's/^/> /'

 # delete leading angle bracket & space from each line (unquote a message)
 sed 's/^> //'

 # remove most HTML tags (accommodates multiple-line tags)
 sed -e :a -e 's/<[^>]*>//g;/</N;//ba'

 # extract multi-part uuencoded binaries, removing extraneous header
 # info, so that only the uuencoded portion remains. Files passed to
 # sed must be passed in the proper order. Version 1 can be entered
 # from the command line; version 2 can be made into an executable
 # Unix shell script. (Modified from a script by Rahul Dhesi.)
 sed '/^end/,/^begin/d' file1 file2 ... fileX | uudecode   # vers. 1
 sed '/^end/,/^begin/d' $* | uudecode                      # vers. 2

 # zip up each .TXT file individually, deleting the source file and
 # setting the name of each .ZIP file to the basename of the .TXT file
 # (under DOS: the "dir /b" switch returns bare filenames in all caps).
 echo @echo off >zipup.bat
 dir /b *.txt | sed "s/^\(.*\)\.TXT/pkzip -mo \1 \1.TXT/" >>zipup.bat


Sed takes one or more editing commands and applies all of them, in sequence, to each line of input. After all the commands have been applied to the first input line, that line is output and a second input line is taken for processing, and the cycle repeats. The preceding examples assume that input comes from the standard input device (i.e, the console, normally this will be piped input). One or more filenames can be appended to the command line if the input does not come from stdin. Output is sent to stdout (the screen). Thus:

 cat filename | sed '10q'        # uses piped input
 sed '10q' filename              # same effect, avoids a useless "cat"
 sed '10q' filename > newfile    # redirects output to disk

For additional syntax instructions, including the way to apply editing commands from a disk file instead of the command line, consult "sed and awk Pocket Reference, 2nd Edition" by Dale Dougherty and Arnold Robbins (O'Reilly, 1997; http://www.ora.com), "UNIX Text Processing," by Dale Dougherty and Tim O'Reilly (Hayden Books, 1987) or the tutorials by Mike Arst distributed in U-SEDIT2.ZIP (many sites). To fully exploit the power of sed, one must understand "regular expressions." For this, see "Mastering Regular Expressions" by Jeffrey Friedl (O'Reilly, 1997). The manual ("man") pages on Unix systems may be helpful.Try "man sed", "man regexp", or the subsection on regular expressions in "man ed", but man pages are notoriously difficult. They are not written to teach sed use or regexps to first-time users, but as a reference text for those already acquainted with these tools.


The preceding examples use single quotes ('...') instead of double quotes ("...") to enclose editing commands, since sed is typically used on a Unix platform. Single quotes prevent the Unix shell from intrepreting the dollar sign ($) and backquotes (`...`), which are expanded by the shell if they are enclosed in double quotes. Users of the "csh" shell and derivatives will also need to quote the exclamation mark (!) with the backslash (i.e., \!) to properly run the examples listed above, even within single quotes. Versions of sed written for DOS invariably require double quotes ("...") instead of single quotes to enclose editing commands.


For clarity in documentation, we have used the expression '\t' to indicate a tab character (0x09) in the scripts. However, most versions of sed do not recognize the '\t' abbreviation, so when typing these scripts from the command line, you should press the TAB key instead. '\t' is supported as a regular expression metacharacter in awk, perl, and in a few implementations of sed.


Versions of sed do differ, and some slight syntax variation is to be expected. In particular, most do not support the use of labels (:name) or branch instructions (b,t) within editing commands, except at the end of those commands. We have used the syntax which will be portable to most users of sed, even though the popular GNU versions of sed allow a more succinct syntax. When the reader sees a fairly long command such as this:

sed -e '/AAA/b' -e '/BBB/b' -e '/CCC/b' -e d

it is heartening to know that GNU sed will let you reduce it to:

sed '/AAA/b;/BBB/b;/CCC/b;d'

In addition, remember that while many versions of sed accept a command like "/one/ s/RE1/RE2/", some do NOT allow "/one/! s/RE1/RE2/", which contains space before the 's'. Omit the space when typing the command.


If execution speed needs to be increased (due to large input files or slow processors or hard disks), substitution will be executed more quickly if the "find" expression is specified before giving the "s/.../.../" instruction. Thus:

sed 's/foo/bar/g' filename         # standard replace command
   sed '/foo/ s/foo/bar/g' filename   # executes more quickly
   sed '/foo/ s//bar/g' filename      # shorthand sed syntax

On line selection or deletion in which you only need to output lines from the first part of the file, a "quit" command (q) in the script will drastically reduce processing time for large files. Thus:

sed -n '45,50p' filename           # print line nos. 45-50 of a file
   sed -n '51q;45,50p' filename       # same, but executes much faster

If you have any additional scripts to contribute or if you find errors in this document, please send e-mail to the compiler. Indicate the version of sed you used, the operating system it was compiled for, and the nature of the problem. Various scripts in this file were written or contributed by: