System call of grep

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December 11th, 2012, 06:58 PM

ngungo

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PHP5 - System call of grep

Hi there,
I wish to use a system call of grep but unable to grep for multiple words though if I tried it from command line it worked fine. The syntax for multiple words grep is:
# grep 'word1\|word2' filename.txt

PHP Code:


		
			
// This statement works perfectly

system("grep 'word' filename.txt");



// None of these works

system("grep 'word1\|word2' filename.txt");

system("grep 'word1\\|word2' filename.txt");

system("grep 'word1/\|word2' filename.txt");

system("grep 'word1&92;&124;word2' filename.txt");

Please help. Thanks in advance.
--ngungo

December 11th, 2012, 08:30 PM

requinix

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Quote:

Originally Posted by ngungo

The syntax for multiple words grep is:
# grep 'word1\|word2' filename.txt

Uh, no? It's

Code:

grep 'word1|word2' filename.txt

The backslash you added escaped the pipe, thus grep would literally look for "word1|word2".

Why they don't work:
1. Backslash
2. Backslash (you escaped the backslash in PHP)
3. Backslash still, but now there's a forward slash in there for some reason
4. Putting aside the fact that those aren't actually valid HTML entities, why the heck would HTML entities give you the result you need? Do you know why they're called "HTML entities"?

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December 11th, 2012, 09:29 PM

ngungo

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Thanks requinix. For quick response.
I have checked carefully and many times that

Code:

grep 'word1|word2' filename.txt

would not work. It's syntactically incorrect.
Here is some reference: http://www.cyberciti.biz/faq/searching-multiple-words-string-using-grep/

Code:

grep 'word1\|word2' filename.txt

Code:

egrep 'word1|word2' filename.txt

would work.

Comments on this post

requinix agrees!

December 11th, 2012, 10:25 PM

requinix

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You can't see me but I have egg on my face. So I may have aliased grep to egrep a long time ago, which would explain why the "master|worker" I searched for today worked. And why I thought that grep worked with the more powerful regular expressions by default and not the ones where | is a simple character and \| is the metacharacter.

Which leaves me with nothing to explain why it doesn't seem to work for you. Particularly when I try it myself.

Code:

$ cat test.txt
foo
bar
baz
$ cat test.php
<?php

system("grep 'foo\|bar' test.txt");

$ php -f test.php
foo
bar
$

December 12th, 2012, 08:09 AM

ngungo

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Thanks!
Solved!

The error I got was in a different aspect.

PHP5 - System call of grep

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