Match exactly (and only) the pattern I specify in a grep command

Usually, grep searches for all lines containing a match for the pattern/parameter I specify.

I would like to match just the pattern (i.e. not the whole line).

So, if a file contains the lines:

We said that we'll come.
Unfortunately, we were delayed.
Now, we're on our way.
Didn't I say we'd come?

I want to find all contractions starting with "we" (regex pattern: we\'[a-z]+/i); I'm looking for the output:

we'll
we're
we'd

How do I do this (with grep or another Unix/Windows command-line tool)?

1

2 Answers

Use the -o option:

grep -E -i -o "we'[a-z]+" file.txt

Note that this is not universally portable to all grep implementations, though.

1

I'd prefer Perl for something like this:

#!/usr/bin/perl
use strict;
use warnings;
open FH, "< parse.txt" or die $!;
while(<FH>)
{ while($_ =~ /\b(we\'\w+)\b/g) { print $1."\n"; }
}
close FH;

Input text:

Some text we're test we'll why we're.
More text we'll we're.
Test.

Output:

we're
we'll
we're
we'll
we're

2

Your Answer

Sign up or log in

Sign up using Google Sign up using Facebook Sign up using Email and Password Submit

Post as a guest

Post Your Answer Discard

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy