Sed

FILE SPACING
double space a file sed G

'''double space a file which already has blank lines in it. Output file should contain no more than one blank line between lines of text.''' sed '/^$/d;G'

triple space a file sed 'G;G'

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

insert a blank line above every line which matches "regex" sed '/regex/{x;p;x;}'

insert a blank line below every line which matches "regex" sed '/regex/G'

insert a blank line above and below every line which matches "regex" sed '/regex/{x;p;x;G;}'

NUMBERING
'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 '$='

TEXT CONVERSION AND SUBSTITUTION
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$//'           # gsed 3.02.80, but top script is easier

IN UNIX ENVIRONMENT: convert Unix newlines (LF) to DOS format sed "s/$/`echo -e \\\r`/"           # command line under ksh sed 's/$'"/`echo \\\r`/"            # command line under bash sed "s/$/`echo \\\r`/"              # command line under zsh sed 's/$/\r/'                       # gsed 3.02.80

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

'IN DOS ENVIRONMENT: convert DOS newlines (CR/LF)'' to Unix format Can only be done with UnxUtils sed, version 4.0.7 or higher. Cannot be done with other DOS versions of sed. Use "tr" instead.''' sed "s/\r//" infile >outfile        # UnxUtils sed v4.0.7 or higher tr -d \r outfile           # GNU tr version 1.22 or higher

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 and 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 sed 's/\(.*\)foo\(.*foo\)/\1bar\2/' # replace the next-to-last case sed 's/\(.*\)foo/\1bar/'           # replace only the last case

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'

change "scarlet" or "ruby" or "puce" to "red" sed 's/scarlet/red/g;s/ruby/red/g;s/puce/red/g'  # most seds gsed 's/scarlet\|ruby\|puce/red/g'               # GNU sed only

reverse order of lines (emulates "tac") bug/feature in HHsed v1.5 causes blank lines to be deleted sed '1!G;h;$!d'              # method 1 sed -n '1!G;h;$p'            # method 2

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/ /'

if a line ends with a backslash, append the next line to it sed -e :a -e '/\\$/N; s/\\\n//; ta'

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'

add commas to numeric strings, changing "1234567" to "1,234,567" gsed ':a;s/\B[0-9]\{3\}\>/,&/;ta'                    # GNU sed sed -e :a -e 's/\(.*[0-9]\)\([0-9]\{3\}\)/\1,\2/;ta' # other seds

add commas to numbers with decimal points and minus signs (GNU sed) gsed ':a;s/\(^\|[^0-9.]\)\([0-9]\+\)\([0-9]\{3\}\)/\1\2,\3/g;ta'

add a blank line every 5 lines (after lines 5, 10, 15, 20, etc) gsed '0~5G'                 # GNU sed only sed 'n;n;n;n;G;'            # other seds

SELECTIVE PRINTING OF CERTAIN LINES
print first 10 lines of file (emulates behavior of "head") sed 10q

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

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

print the last 2 lines of a file (emulates "tail -2") sed '$!N;$!D'

print the last line of a file (emulates "tail -1") sed '$!d'                   # method 1 sed -n '$p'                 # method 2

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 the line immediately before a regexp, but not the line containing the regexp sed -n '/regexp/{g;1!p;};h'

print the line immediately after a regexp, but not the line containing the regexp sed -n '/regexp/{n;p;}'

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   # most seds gsed '/AAA\|BBB\|CCC/!d'                       # GNU sed only

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;$!d;}' -e 'x;/AAA/b' -e '/BBB/b' -e '/CCC/b' -e d gsed '/./{H;$!d;};x;/AAA\|BBB\|CCC/b;d'        # GNU sed only

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

beginning at line 3, print every 7th line gsed -n '3~7p'              # GNU sed only sed -n '3,${p;n;n;n;n;n;n;}' # other seds

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

SELECTIVE DELETION OF CERTAIN LINES
print all of file EXCEPT section between 2 regular expressions sed '/Iowa/,/Montana/d'

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

'''delete duplicate, nonconsecutive lines from a file. Beware not to overflow the buffer size of the hold space, or else use GNU sed.''' sed -n 'G; s/\n/&&/; /^\([ -~]*\n\).*\n\1/d; s/\n//; h; P'

delete all lines except duplicate lines (emulates "uniq -d"). sed '$!N; s/^\(.*\)\n\1$/\1/; t; D'

delete the first 10 lines of a file sed '1,10d'

delete the last line of a file sed '$d'

delete the last 2 lines of a file sed 'N;$!P;$!D;$d'

delete the last 10 lines of a file sed -e :a -e '$d;N;2,10ba' -e 'P;D'  # method 1 sed -n -e :a -e '1,10!{P;N;D;};N;ba' # method 2

delete every 8th line gsed '0~8d'                          # GNU sed only sed 'n;n;n;n;n;n;n;d;'               # other seds

delete ALL blank lines from a file (same as "grep '.' ") sed '/^$/d'                          # method 1 sed '/./!d'                          # method 2

delete all CONSECUTIVE blank lines from file except the first; alsodeletes 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 '/./,$!d' delete all trailing blank lines at end of file sed -e :a -e '/^\n*$/{$d;N;ba' -e '}' # works on all seds sed -e :a -e '/^\n*$/N;/\n$/ba'       # ditto, except for gsed 3.02*

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

SPECIAL APPLICATIONS
'''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

TYPICAL USE
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 & awk, 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 "maned"), 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.

QUOTING SYNTAX
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.

USE OF '\t' IN SED SCRIPTS
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 HHsed, sedmod, and GNU sed v3.02.80.

VERSIONS 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'     # or even sed '/AAA\|BBB\|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.

OPTIMIZING FOR SPEED
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