Handy one-liners for sed

# 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'

### 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/.$//'

# 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/ /'

### 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 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 or BBB or CCC (emulates "egrep")
sed -e '/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

### SELECTIVE DELETION OF CERTAIN LINES:

# 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'

### SPECIAL APPLICATIONS

# remove nroff overstrikes (char, backspace) from man pages
sed "s/.`echo \\\b`//g" # double quotes required for Unix environment
sed 's/.\x08//g' # hex expression for GNU sed (octal is "\010")

# 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;s/\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 "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.

# 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 in a few implementations of sed.

# 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'

# 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

# strip all html tags (http://tealscientific.com/blog/?p=201)
sed 's/<[^>]*>//g' filename

# HANDY ONE-LINERS FOR SED
# http://www.unixguide.net/unix/sedoneliner.shtml