Is there a command that allows searching a keyword in files under a directory with specific extension ?

The string grep -irn "string" ./path gives a recursive search for all files under the directory./path. My specific requirement is to search in all files under ./path with an extension such as *.h


After some trials, I think grep -irn 'string' --include '*.h' is more handy


Set (turn on) the shell option globstar with the command

    shopt -s globstar

This will cause ** as a filename component to mean everything here and below.  So path/** means everything in the path directory and its subdirectories.  (You don't need to type ./ here.)  Then you can use

grep -in "string" path/**/*.h

to search all the .h files in and under path.

You can unset options with shopt -u.

find /path -iname "*.h" -exec grep -inH "string" "{}" \;

If you can install something on your machine, I suggest using ack.

You can do exactly what you need with it and much more. For your use case, you can do:

# Depending of your system, you have to use one or the other
ack --hh -i string path
ack-grep --hh -i string path
  • --hh filters on h files
  • -i ignores the case

To find which file filters are supported natively, run the command ack --help=type.

  • There's also ag, a former clone of ack. Former, because their feature sets have since diverged somewhat. – 8bittree Sep 28 '16 at 17:24
  • I didn't know ag. Thanks for sharing. – A.D. Sep 29 '16 at 6:58

What about this one?

find -L ./path -name "*.h" -exec grep -in "string" {} \;


  • -L : follow symlinks
  • -name : using the asterisk, you can describe extensions
  • -in : same as your proposal, but the 'r' is replaced by the find command
  • {} : this stands for the result of the find command
  • \; : in case you combine find with -exec, this is the end-of-command specifier
  • 1
    How does "*.h" work? I would have thought it needed to be '*.h' – Joe Sep 13 '16 at 7:15
  • I always work with double quotes, I don't think it makes a difference. – Dominique Sep 13 '16 at 7:22

If you're using gnu grep then it's got a flag that does exactly what you want:

grep -irn --include=\*.h "string" path

although I don't think it's available in other greps.

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