3.2. Common one-line sed scripts

A separate document of over 70 handy "one-line" sed commands is available at

       https://sed.sourceforge.net/sed1line.txt

Here are several common sed commands for one-line use. MS-DOS users should replace single quotes ('...') with double quotes ("...") in these examples. A specific filename usually follows the script, though the input may also come via piping or redirection.

   # Double space a file
   sed G file

   # Triple space a file
   sed 'G;G' file

   # 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

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

   # 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

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

   # Delete BOTH leading and trailing whitespace from each line
   sed 's/^[ ^t]*//;s/[ ^]*$//' file    # see note on '^t', above

   # 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

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

   # 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

   # Delete all leading blank lines at top of file (only).
   sed '/./,$!d' file

   # Delete all trailing blank lines at end of file (only).
   sed -e :a -e '/^\n*$/{$d;N;};/\n$/ba' file

   # If a line ends with a backslash, join the next line to it.
   sed -e :a -e '/\\$/N; s/\\\n//; ta' file

   # 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