How can I recursively grep through sub-directories?

You must mean that your ancient Unix doesn't have GNU grep, right? If you do, just go do a "man grep"; you don't need to read this (though you may want to just so you really appreciate GNU grep). Just add "-r" and grep will search through subdirectories.

But if you are on some old Unix without this, it gets very hard. The problem with all the reponses that invariably pop up for this type of question is that none of them are ever truly fast and most of them aren't truly robust.

November, 2008: Excuse the interuption, but there is something new to talk about and I didn't want you to have to go all the way to the comments to find it. It's called "ack", it's written in Perl, and it addresses the things the things this page talks about. Find it at http://petdance.com/ack/.

Typically, the answer is to use find, xargs, and grep. That's horribly slow for a full filesystem search, and it's painfully difficult to properly construct a pipeline that will avoid searching binaries if you don't want to, won't get stuck on named pipes or blow up on funky filenames (beginning with -, or sometimes spaces, punctuation etc). There are ways around all these things, but they are all ugly.

BTW, something that almost never gets mentioned but that I will frequently use under conditions where it is appropriate is a simple

 
 grep pattern * */* */*/* 2>/dev/null
 

Not useful much beyond that, and may not even be good at that except for certain starting points, but it's faster than any find xargs pipeline can ever be if the set is small enough.

The simplistic approach using find is

 find /whereveryouwantostart -exec grep whatever {} dev/null \;
 

That's not necessarily very efficient. Using xargs can help

 find . | xargs grep whatever
 

But it also has bugs if the filenames could have "-" at their beginning. Fixing that can be a little nasty.

You may not want to grep binary files:

 find .  -type f -print|xargs file|grep -i text|cut -fl -d:    | xargs grep whatever
 

That's pretty awful, but it's what you have to get into if you have special cases. Special cases are what makes this question more difficult. If you have a small number of files and subdirs to search, the simple approach may work fine for you. If not, you have to get more creative.

Bill Campbell offers this Perl script:

 I have a perlscript I call ``textfiles'' that I use for many
 things like this:
        textfiles dirname [dirname... ] | xargs ...
 
 Essentially it runs ``gfind @ARGV -type f'', then uses perl's -T
 option on each file to determine whether it's a text file.
 
 My textfiles script also has options to add options to the gnu
 find command like -xdev, -mindepth, and -maxdepth.
 
 Hell, it's short so I'm attaching it for anybody who wants to use
 it.  It does assume that the gnu version of find is in your PATH
 named gfind (I make a symlink to /usr/bin/find on Linux systems
 so that it works there as well).
 
 
 #!/usr/local/bin/perl
 eval ' exec /usr/local/bin/perl -S $0 "$@" '
        if $running_under_some_shell;
 
 # $Header: /u/usr/cvs/lbin/textfiles,v 1.7 2000/06/22 18:29:08 bill Exp $
 # $Date: 2000/06/22 18:29:08 $
 # @(#) $Id: textfiles,v 1.7 2000/06/22 18:29:08 bill Exp $
 # 
 #      find text files
 
 ( $progname = $0 ) =~ s!.*/!!; # save this very early
 
 $USAGE = "
 # Find text files
 #
 #   Usage: $progname [-v] [file [file...]]
 #
 # Options   Argument    Description
 #   -f                  Follow symlinks
 #   -M      maxdepth    maxdepth argument to gfind
 #   -m      mindepth    mindepth argument to gfind
 #   -x                  Don't cross device boundaries
 #   -v                  Verbose
 #
 ";
 
 sub usage {
        die join("\n",@_) .
        "\n$USAGE\n";
 }
 
 do "getopts.pl";
 
 &usage("Invalid Option") unless do Getopts("fM:m:xvV");
 
 $verbose = '-v' if $opt_v;
 $suffix = $$ unless $opt_v;
 
 $\ = "\n";     # use newlines as separators.
 
 # use current directory if there aren't any arguments
 push(@ARGV, '.') unless defined($ARGV[0]);
 
 $args = join(" ", @ARGV);
 $xdev = '-xdev' if $opt_x;
 $opt_f = '-follow' if $opt_f;
 $opt_m = "-mindepth $opt_m" if $opt_m;
 $opt_M = "-maxdepth $opt_M" if $opt_M;
 $cmd = "gfind @ARGV -type f $xdev $opt_f $opt_m $opt_M |";
 print STDERR "cmd = >$cmd<" if $verbose;
 
 open(INPUT, $cmd);
 while(<INPUT>) {
        chop($name = $_);
        print STDERR "testing $name..." if $verbose;
        print $name if -T $name;
 }
 
 

John Dubois also comments on Glimpse:

Glimpse indexes files by the words contained in the file. Then when you want to search all of the files, it only runs its equivalent of grep (agrep) on the files that contain the words you're looking for. You can search for partial words too, though it takes longer. I have the man pages, include files, rfcs, source trees, my home directory, web pages, etc. all separately glimpse-indexed.

Binaries & man pages for OpenServer are at ftp://deepthought.armory.com/pub/scobins/glimpse.tar.Z

A front end that allows you to easily search any of multiple glimpse databases is at: ftp://ftp.armory.com/pub/scripts/search

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Thu Feb 28 20:45:18 2008: Subject: to recrusively grep in unix   duraimuthu


to recrusively grep in unix
create the following shell script. run it with a parameter like './new.sh string'

#!/bin/bash
for i in $( du -a | awk '{print $2}' ); do
grep $1 $i
done




Thu Feb 28 21:00:13 2008: Subject:   TonyLawrence


Goodness: isn't "du" a bit much just to get a list of file names?

Example

time du -a

real 0m10.676s user 0m0.395s sys 0m5.512s

time find .

real 0m1.272s user 0m0.192s sys 0m0.698s

Also: that's going to run into problems with odd file names (just as find and xargs do). Really it's no different (other than being slow) than the "find" example without "xargs" given above, and of course "xargs" makes that much more efficient - but still suffers from the various problems covered above.

On Mac OS X, "mdfind" answers *most* situations, but not all..

Recursive grep remains difficult and problematical.









Tue Jul 1 19:06:32 2008: Subject: grep recursively   anonymous


This is much more efficient, the wildcards in grep might not work as nicely as they do for find

find <path> -name <filenamepattern> | xargs grep <searchstring>



Tue Jul 1 21:34:41 2008: Subject:   TonyLawrence


Sigh.. did you even READ the article?



Wed Nov 26 23:41:43 2008: Subject:   TonyLawrence


Whoopee: something new, and it's GREAT!

http://petdance.com/ack/

Found at http://mike.hostetlerhome.com/ ("Where Are The Wise Men?")

Thanks, Mike!



Sat Nov 29 01:01:35 2008: Subject:   AlexWorden


Ummm... how about:



grep -RH --include "abc.foo" searchTerm *



-R tells grep to search recursively

-H tells grep to print out the filename it found a match in (how retarded is it that this isn't the default!)

--include lets you specify filename patterns you want to search



You'll need to supply the * pattern at the end to cause grep to include everything in the current directory and below in it's search - otherwise it'll wait for std input.





Sat Nov 29 01:20:43 2008: Subject:   TonyLawrence


If you read the entire article you'd understand that no matter WHAT you do, recursive grep is difficult.

---

My Unix/Linux Troubleshooting Book

My Hard Truths about Easy Money Book

My Self Employment Book

---

Wed Dec 10 14:49:20 2008: Subject:   anonymous


I used this one for finding expressions in sql scripts:
find . -name "*.sql" -print0 -type f | xargs -0 grep "expression"

Read the "UNUSUAL FILENAMES" section in find's manpage




Tue Mar 24 03:03:17 2009: Subject: Did any of you actually *read* the entire article?   anonymous


The article is based on the premise that some UNIX systems don't have GNU tools available (i.e. Solaris), thus things like grep -R, or find -print0 and xargs -0 are also not available.

Nice article.



Tue Mar 24 12:01:50 2009: Subject:   TonyLawrence


Well, heck: all they had to do was read the first paragraph :-)





Thu May 28 11:30:01 2009: Subject:   anonymous


Many thanks to Alex Worden for giving the example for using grep -r (very strange syntax).

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