How to do a recursive find/replace of a string with awk or sed?

find /home/www \( -type d -name .git -prune \) -o -type f -print0 | xargs -0 sed -i 's/subdomainA\.example\.com/subdomainB.example.com/g'

-print0 tells find to print each of the results separated by a null character, rather than a new line. In the unlikely event that your directory has files with newlines in the names, this still lets xargs work on the correct filenames.

\( -type d -name .git -prune \) is an expression which completely skips over all directories named .git. You could easily expand it, if you use SVN or have other folders you want to preserve -- just match against more names. It's roughly equivalent to -not -path .git, but more efficient, because rather than checking every file in the directory, it skips it entirely. The -o after it is required because of how -prune actually works.

For more information, see man find.

The simplest way for me is

grep -rl oldtext . | xargs sed -i 's/oldtext/newtext/g'

Note: Do not run this command on a folder including a git repo - changes to .git could corrupt your git index.

find /home/www/ -type f -exec \    sed -i 's/subdomainA\.example\.com/subdomainB.example.com/g' {} +

Compared to other answers here, this is simpler than most and uses sed instead of perl, which is what the original question asked for.