Why does this regex in bash not match the line despite matching in regex tester?

Question

I am trying to match a line in netstat where the local port matches some port that's passed in to my script. But this regex (while it matches in a regex tester) doesn't seem to work.

# Get lines from netstat
IFS=$'\r\n' GLOBIGNORE='*' command eval  'NetstatLines=($(netstat -anq))'

for line in "${NetstatLines[@]}"; do

    # This never matches
    if [[ "$line" =~ ^\s*(TCP|UDP)\s+(\d+\.\d+\.\d+\.\d+:$iPort|\[::\d*\]:$iPort)\s+ ]]; then
        echo "found it!!"
    fi

done

The lines look like:

Active Connections

  Proto  Local Address          Foreign Address        State
  TCP    0.0.0.0:135            0.0.0.0:0              LISTENING
  TCP    0.0.0.0:445            0.0.0.0:0              LISTENING
  TCP    0.0.0.0:623            0.0.0.0:0              LISTENING
  TCP    0.0.0.0:2179           0.0.0.0:0              LISTENING
  TCP    0.0.0.0:5040           0.0.0.0:0              LISTENING
  TCP    0.0.0.0:7680           0.0.0.0:0              LISTENING

So if $iPort is 135, it should match the 4th line.

Just search for "posix extended regular expression" and you'll find plenty. — Shawn, Jul 31 '19 at 00:43
@Shawn I did but I cannot find enough information on how to translate my current regex to a posix one. — Don Rhummy, Jul 31 '19 at 00:50
POSIX RE syntax doesn't support the `\d` and `\s` shortcuts; use `[[:digit:]]` and `[[:space:]]` instead. — Gordon Davisson, Jul 31 '19 at 01:04

score 0 · Answer 1 · answered Jul 31 '19 at 01:01

Thanks to @Shawn and these sites:

I was able to figure it out:

^[[:space:]]*(TCP|UDP)[[:space:]]+([[:digit:]]+[.][[:digit:]]+[.][[:digit:]]+[.][[:digit:]]+:$iPort|[[]::[[:digit:]]*[]]:$iPort)

That is equivalent to the non-posix version I started with.

Why does this regex in bash not match the line despite matching in regex tester?

1 Answers1