Question

I am trying to give grep a regex pattern for screen resolution(e.g. 1280x720) as following

[0-9]{3,}x[0-9]{3,}

but it doesn’t seem to be working.

The following works but that doesn’t translate to the above one.

[0-9][0-9][0-9][0-9]*x[0-9][0-9][0-9][0-9]*

Answer 1

Your regex seems fine for bash :

[[ 1280x720 =~ [0-9]{3,}x[0-9]{3,} ]] && echo OK
OK

If you want to use grep :

$ cat B
640x480
$
$ grep -c "[0-9]\{3,\}x[0-9]\{3,\}" B
1
$
$ grep --version
grep (GNU grep) 2.14