3.1. More detailed explanation of basic sed

Sed takes a script of editing commands and applies each command, in order, to each line of input. After all the commands have been applied to the first line of input, that line is output. A second input line is taken for processing, and the cycle repeats. Sed scripts can address a single line by line number or by matching a /RE pattern/ on the line. An exclamation mark '!' after a regex ('/RE/!') or line number will select all lines that do NOT match that address. Sed can also address a range of lines in the same manner, using a comma to separate the 2 addresses.

     $d               # delete the last line of the file
     /[0-9]\{3\}/p    # print lines with 3 consecutive digits
     5!s/ham/cheese/  # except on line 5, replace 'ham' with 'cheese'
     /awk/!s/aaa/bb/  # unless 'awk' is found, replace 'aaa' with 'bb'
     17,/foo/d        # delete all lines from line 17 up to 'foo'

Following an address or address range, sed accepts curly braces '{...}' so several commands may be applied to that line or to the lines matched by the address range. On the command line, semicolons ';' separate each instruction and must precede the closing brace.

     sed '/Owner:/{s/yours/mine/g;s/your/my/g;s/you/me/g;}' file

Range addresses operate differently depending on which version of sed is used (see section 3.4, below). For further information on using sed, consult the references in section 2.3, above.