how do i replace this text in a file from the command line in linux?

Question

hi! i have a proxy config file which has the following line:

Allow 212.21.3.44

i'd like to replace that ip address portion with my new ip address when it changes. it would probably be easier to just use the line number when searching for it - i don't think that config file will change at all other than that particular setting.

how can i do it from the command line with something like like perl, sed, etc?

thanks!

Answer 1

sed -i 's/[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}/my.new.ip.here/' file.txt

The -i flag will change the file in place (depends on your distro/flavor of *nix - works on Ubuntu for me).

Answer 2

If you want to use sed to change a specific line number, you could use:

sed -i '<line number> s/Allow .*$/Allow <new ip>/g' <filename>

Answer 3

in case line number does change

sed -i '/Allow/s/Allow .*$/Allow <new ip>/' <filename>