Find and Replace across multiple files in Linux

For example, do this (Courtesy Rushi):
find mydir -name "*.tex" | xargs sed -i 's/foo/bar/g'
This replaces `foo' by `bar' in all .tex files in the directory mydir and its subdirectories.

This is useful for changes to latex code stored in a directory structure, since
find: gets the correct recursive file listing
-i: edit the files in place
/g: replace all occurrences in the file (globally)
foo: is a regular expression (POSIX.2 BRE)

[search tex]