How to match once per file in grep?

Question

Is there any grep option that let's me control total number of matches but stops at first match on each file?

Example:

If I do this grep -ri --include '*.coffee' 're' . I get this:

./app.coffee:express = require 'express'
./app.coffee:passport = require 'passport'
./app.coffee:BrowserIDStrategy = require('passport-browserid').Strategy
./app.coffee:app = express()
./config.coffee:    session_secret: 'nyan cat'

And if I do grep -ri -m2 --include '*.coffee' 're' ., I get this:

./app.coffee:config = require './config'
./app.coffee:passport = require 'passport'

But, what I really want is this output:

./app.coffee:express = require 'express'
./config.coffee:    session_secret: 'nyan cat'

Doing -m1 does not work as I get this for grep -ri -m1 --include '*.coffee' 're' .

./app.coffee:express = require 'express'

Tried not using grep e.g. this find . -name '*.coffee' -exec awk '/re/ {print;exit}' {} \; produced:

config = require './config'
    session_secret: 'nyan cat'

UPDATE: As noted below the GNU grep -m option treats counts per file whereas -m for BSD grep treats it as global match count

Answer 1

So, using grep, you just need the option -l, --files-with-matches.

All those answers about find, awk or shell scripts are away from the question.

Answer 2

find . -name \*.coffee -exec grep -m1 -i 're' {} \;

find's -exec option runs the command once for each matched file (unless you use + instead of \;, which makes it act like xargs).

Answer 3

I think you can just do something like

grep -ri -m1 --include '*.coffee' 're' . | head -n 2

to e.g. pick the first match from each file, and pick at most two matches total.

Note that this requires your grep to treat -m as a per-file match limit; GNU grep does do this, but BSD grep apparently treats it as a global match limit.

Answer 4

I would do this in awk instead.

find . -name \*.coffee -exec awk '/re/ {print FILENAME ":" $0;exit}' {} \;

If you didn't need to recurse, you could just do it with awk:

awk '/re/ {print FILENAME ":" $0;nextfile}' *.coffee

Or, if you're using a current enough bash, you can use globstar:

shopt -s globstar
awk '/re/ {print FILENAME ":" $0;nextfile}' **/*.coffee

Answer 5

You can do this easily in perl, and no messy cross platform issues!

use strict;
use warnings;
use autodie;

my $match = shift;

# Compile the match so it will run faster
my $match_re = qr{$match};

FILES: for my $file (@ARGV) {
    open my $fh, "<", $file;

    FILE: while(my $line = <$fh>) {
        chomp $line;

        if( $line =~ $match_re ) {
            print "$file: $line\n";
            last FILE;
        }
    }
}

The only difference is you have to use Perl style regular expressions instead of GNU style. They're not much different.

You can do the recursive part in Perl using File::Find, or use find feed it files.

find /some/path -name '*.coffee' -print0 | xargs -0 perl /path/to/your/program

Answer 6

using find and xargs. find every .coffee files and excute -m1 grep to each of them

find . -print0 -name '*.coffee'|xargs -0 grep -m1 -ri 're'

test without -m1

linux# find . -name '*.txt'|xargs grep -ri 'oyss'
./test1.txt:oyss
./test1.txt:oyss1
./test1.txt:oyss2
./test2.txt:oyss1
./test2.txt:oyss2
./test2.txt:oyss3

add -m1

linux# find . -name '*.txt'|xargs grep -m1 -ri 'oyss'
./test1.txt:oyss
./test2.txt:oyss1