How to grep and replace

I need to recursively search for a specified string within all files and subdirectories within a directory and replace this string with another string.

I know that the command to find it might look like this:

grep 'string_to_find' -r ./*

But how can I replace every instance of string_to_find with another string?

Another option is to use find and then pass it through sed.

find /path/to/files -type f -exec sed -i 's/oldstring/new string/g' {} \;

I got the answer.

grep -rl matchstring somedir/ | xargs sed -i 's/string1/string2/g'

You could even do it like this:

Example

grep -rl 'windows' ./ | xargs sed -i 's/windows/linux/g'

This will search for the string 'windows' in all files relative to the current directory and replace 'windows' with 'linux' for each occurrence of the string in each file.

This works best for me on OS X:

grep -r -l 'searchtext' . | sort | uniq | xargs perl -e "s/matchtext/replacetext/" -pi

Source: http://www.praj.com.au/post/23691181208/grep-replace-text-string-in-files