Regular Expression Pocket Reference, 2nd Edition

Name

sed

sed '[address1][,address2]s/pattern/replacement/[flags]' files
sed -f script files

By default, sed applies the substitution to every line in files. Each address can be either a line number, or a regular expression pattern. A supplied regular expression must be defined within the forward slash delimiters (/ . . . /).

If address1 is supplied, substitution will begin on that line number, or the first matching line, and continue until either the end of the file, or the line indicated or matched by address2. Two subsequences, & and \n, will be interpreted in replacement based on the match results.

The sequence & is replaced with the text matched by pattern. The sequence \n corresponds to a capture group (1 . . . 9) in the current match. Here are the available flags:

n

Substitute the nth match in a line, where n is between 1 and 512.

g

Substitute all occurrences of pattern in a line.

p

Print lines with successful substitutions.

wfile

Write lines with successful substitutions to file.

Example

Change date formats from MM/DD/YYYY to DD.MM.YYYY.

$ echo 12/30/1969' |
 sed 's!\([0-9][0-9]\)/\([0-9][0-9]\)/\([0-9]\{2,4\}\)!
\2.\1.\3!g'