Why does my script not work on FreeBSD? (awk: syntax error)

Why does this script not work on FreeBSD? I ran the script on Centos and Debian, all was fine. On FreeBSD (10.2) I encounter the following error:

awk: syntax error at source line 1
 context is
    match($0, "^listen >>>  queue:[[:space:]]+(.*)", <<< 
awk: bailing out at source line 1
-0.9902

As an example, here is some output of php-form status:

pool:                 www
process manager:      ondemand
start time:           29/Feb/2016:15:18:54 +0200
start since:          2083770
accepted conn:        1467128
listen queue:         0
max listen queue:     129
listen queue len:     128
idle processes:       1
active processes:     2
total processes:      3
max active processes: 64
max children reached: 1
slow requests:        0

On Centos and Debian, when I run:

/path/to/script/php-fpm-check.sh "idle processes" http://127.0.0.1/status

I get 1, but on FreeBSD the error mentioned above.

Note: to avoid having to get above script working, here is a quick script which replicates the problem:

echo 'listen queue: 0' | awk '
  match($0, "^listen queue:[[:space:]]+(.*)", a) {
    print a[1]
  }'

Solution

The 3-argument form of match is a GNU awk extension (docs). You'll have to find another way to capture the match (perhaps using the RSTART and RLENGTH variables set as a side-effect of match()), or install gawk on your freebsd system.