December 30, 2018

Sed & Regexp Cheatsheet

Name	Command
Update with auto backup	`sed -i.bak 's/localhost/myhost/g' my-file`, `ls my-file*`, Link: my-file
Use variables in sed	newip=’127.0.1.1′; `sed -i "s/127.0.0.1/$newip/g" my-file` Link: unix.com
Only replace the first match	`sed -i '0,/localhost/{s/localhost/newstring/}' my-file` Link: stackoverflow
Replace multiple lines	`sed -i ':a;N;$!ba;s/Host.*localhost//g' my-file` Link: stackexchange
Add a new line to 3th line	`sed -i "3i mynew string" my-file`
Insert a line of text before a line	`sed -i '/KUBELET_NETWORK_ARGS/i newline' my-file`

Name	Command
Replace string	`sed -i 's/127.0.0.1/127.0.1.1/g' my-file` Link: my-file
Use a different seperator	`sed -i 's#127.0.0.1#127.0.1.1#g' my-file`
Use a different seperator	`sed -i 's#https://www.test.com/test#http://www.try.com#g' my-file`
Delete pattern	`sed '/KUBELET_NETWORK_ARGS.*/d' my-file`
Delete matched lines	`sed -i 's/.KUBELET_NETWORK_ARGS.//g' my-file`
Delete whitespace	`sed -i 's/ //g' my-file`
Delete empty lines	`sed -i '/^$/d' my-file`
Delete 2nd to 4th lines	`sed -i '2,4d' my-file`
Delete leading whitespace	`sed -i 's/^[ \t]*//' my-file`
Delete trailing whitespace	`sed -i 's/[ \t]*$//' my-file`

Name	Command
Insert string to the begining of lines	`sed -i 's/^/head /g' my-file`
Insert string to the end of lines	`sed -i 's/$/ tail/g' my-file`
Add content after nth line	`sed -n -i 'p;3a "new string"' my-file`, `cat -n my-file` Link: unix.com
Add a new line to 3rd line	`sed -i "3i mynew string" my-file`
Insert a line of text before a line	`sed -i '/KUBELET_NETWORK_ARGS/i newline' my-file`