php - comm command to get common data from file1 file2 -

i want common data present in file1 , file2.

<?php      $cmd="comm -12 <(sort /source/20-07-2015/file1 | uniq) <(sort /source/20-07-2015/file2 | uniq) > /20-07-2015/commondata_20072015-248932-ac.csv";     $result =exec($cmd);  ?> 

but above code throwing error:

sh: -c: line 0: syntax error near unexpected token `(' 

php exec() uses sh , sh not support <(...).

the simplest fix (from knows sh/bash not php) have sh invoke bash run command:

$cmd="bash -c 'comm -12 <(sort /source/20-07-2015/file1 | uniq) <(sort /source/20-07-2015/file2 | uniq) > /20-07-2015/commondata_20072015-248932-ac.csv'";