Question

I’m using the following regular expression with the preg_match function in PHP to match the output of the df command in Linux. Note that I used a define macro to simplify the readability of the regular expression.

define("MATCH_DF",
    "/^(?P<filesystem>[0-9a-z\/]+)\s+" . 
    "(?P<blocks>[0-9]+)\s+" . 
    "(?P<used>[0-9]+)\s+" . 
    "(?P<avail>[0-9]+)\s+" . 
    "(?P<percent>[0-9]+%)\s+" .
    "(?P<mount>[0-9a-zA-Z\/]+)\s+$/");

For those who do not know, the output of the df command line looks like this…

Filesystem       1K-blocks      Used Available Use% Mounted on
/dev/sda2        236520176   2863468 221642116   2% /

Can anyone tell me what I’m missing here? Why isn’t this working? I’ve narrowed the problem down to being something in my regular expression.

Answer 1

You are looking for some whitespace at the end of the string, of which there isn’t any. You could swap the + quantifier for a * to make it optional, or remove it all together.

Try this regex…

define("MATCH_DF",
    "/^(?P<filesystem>[\da-z\/]+)\s+" . 
    "(?P<blocks>\d+)\s+" . 
    "(?P<used>\d+)\s+" . 
    "(?P<avail>\d+)\s+" . 
    "(?P<percent>\d+%)\s+" .
    "(?P<mount>[\da-zA-Z\/]+)$/");

CodePad.

I also swapped your [0-9] for \d.

If you want to discard the numeric matches and just keep the named capturing groups…

$matches = array_diff_key($matches, array_values($matches));

CodePad.