sed Commands Cheat Sheet

Monday, February 1, 2016

sed is an extremely powerful stream editor. The web is full of useful sed one liners.

This post will be an ever growing list of sed one liners I have found useful.

Find and Replace

Find and remove all instances of TEXT:

sed 's/TEXT//g'

Find and remove all spaces:

sed -e 's/ //g'

Delete all blank lines from a file

sed '/^$/d' <FILE>

Delete leading whitepsace from front of each line

sed 's/^[ \t]*//' <FILE>

Delete trailing whitespace from end of each line

sed 's/[ \t]*$//' <FILE>

Delete leading and trailing whitespace from each line

sed 's/^[ \t]*//;s/[ \t]*$//' <FILE>

Insert a line of text before a line

sed -i '/PATTERN/i REPLACEWITH' <FILE>

Change configuration file values

Change BRIDGE_HOTPLUG=yes to BRIDGE_HOTPLUG=no no matter what it is already set to:

sed '/BRIDGE_HOTPLUG=/ s/=.*/=no/' /etc/default/bridge-utils

Change PermitRootLogin no to PermitRootLogin yes no matter what it is already set to:

sed '/PermitRootLogin / s/ .*/ yes/' /etc/ssh/sshd_config

Wrap Value in Double Quotes

Change date=2015 to date=”2015”:

echo 'date=2015' | sed 's/\(=[[:blank:]]*\)\(.*\)/\1"\2"/'

Remove word wrap

sed -e :a -e '$!N;s/\n //;ta' -e 'P;D' <FILE>
sed -n 's/.*href="\([^"]*\).*/\1/p' <FILE.html>

Lower case all href=”*” tags

sed -e 's/\(href="\([^"]*\)"\)/\L\1/' <FILE>

Lower case all img src=”*” tags

sed -e 's/\(img src="\([^"]*\)"\)/\L\1/' <FILE>

Lower case all href=”” tags but exclude href=”http” tags

sed -e '/\(href="http"*\)/!s/\(href="\([^"]*\)"\)/\L\1/' <FILE>

Lower case all img src=”” tags but exclude img src=”http” tags

sed -e '/\(img src="http"*\)/!s/\(img src="\([^"]*\)"\)/\L\1/' <FILE>

Remove ‘%20’ only from lines matching href=”*”

sed -e '/\(href="\([^"]*\)"\)/s/%20//g' <FILE>

References

Add quotes around a value using sed

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