To search for files based on their contents, you can use the
grep program. For example, to find out which C source files in
the current directory contain the string ‘thing’, you can do:
grep -l thing *.[ch]
If you also want to search for the string in files in subdirectories,
you can combine grep with find and xargs, like
this:
find . -name '*.[ch]' | xargs grep -l thing
The ‘-l’ option causes grep to print only the names of
files that contain the string, rather than the lines that contain it.
The string argument (‘thing’) is actually a regular expression,
so it can contain metacharacters. This method can be refined a little
by using the ‘-r’ option to make xargs not run grep
if find produces no output, and using the find action
‘-print0’ and the xargs option ‘-0’ to avoid
misinterpreting files whose names contain spaces:
find . -name '*.[ch]' -print0 | xargs -r -0 grep -l thing
For a fuller treatment of finding files whose contents match a
pattern, see the manual page for grep.