3.1 sed script overview

A sed program consists of one or more sed commands, passed in by one or more of the -e, -f, --expression, and --file options, or the first non-option argument if zero of these options are used. This document will refer to “the” sed script; this is understood to mean the in-order concatenation of all of the scripts and script-files passed in. See Overview.

sed commands follow this syntax:

[addr]X[options]

X is a single-letter sed command. [addr] is an optional line address. If [addr] is specified, the command X will be executed only on the matched lines. [addr] can be a single line number, a regular expression, or a range of lines (see sed addresses). Additional [options] are used for some sed commands.

The following example deletes lines 30 to 35 in the input. 30,35 is an address range. d is the delete command:

sed '30,35d' input.txt > output.txt

The following example prints all input until a line starting with the word ‘foo’ is found. If such line is found, sed will terminate with exit status 42. If such line was not found (and no other error occurred), sed will exit with status 0. /^foo/ is a regular-expression address. q is the quit command. 42 is the command option.

sed '/^foo/q42' input.txt > output.txt

Commands within a script or script-file can be separated by semicolons (;) or newlines (ASCII 10). Multiple scripts can be specified with -e or -f options.

The following examples are all equivalent. They perform two sed operations: deleting any lines matching the regular expression /^foo/, and replacing all occurrences of the string ‘hello’ with ‘world’:

sed '/^foo/d ; s/hello/world/' input.txt > output.txt

sed -e '/^foo/d' -e 's/hello/world/' input.txt > output.txt

echo '/^foo/d' > script.sed
echo 's/hello/world/' >> script.sed
sed -f script.sed input.txt > output.txt

echo 's/hello/world/' > script2.sed
sed -e '/^foo/d' -f script2.sed input.txt > output.txt

Commands a, c, i, due to their syntax, cannot be followed by semicolons working as command separators and thus should be terminated with newlines or be placed at the end of a script or script-file. Commands can also be preceded with optional non-significant whitespace characters. See Multiple commands syntax.