This is my first post here, I have a question about something I can't explain.

I'm pretty sure I know what I did wrong, I'm just not 100% sure why it was wrong and wanted to clarify to better my understanding of regex in perl, as I'm fairly inexperienced and looking to improve.

I was searching for vlan ids for removal in the output of "ip addr" in the following way.

my $ethernet=`ip addr`;
if ($ethernet!~/eth1\.\d{4}\@/gm){
    print "No vlans exist on device.\n";
    exit;
}
while ($ethernet=~/(eth1\.\d{4})\@/gm) {
    print `ip link del $1\n";
    print "Removed $1\n";
}

[download]

Doing this as above mostly worked, but it would always miss the first entry for no reason I can explain. So if there were 25 vlan entries in the string from 1001 to 1025 it would match and delete 1002-1025 without fail, and miss 1001 every time.

Changing line 2 to:

if ($ethernet!~/eth1\.\d{4}\@/){

Does what I intended to do.

I had the same problem with a similar line I was using to scrub IP addresses off the vlan devices again missing the first match, I just don't understand why the while loop breaks in the way it does because of the /gm flag on the preceeding if statements match, and was hoping someone could explain. Thanks in advance.

In reply to A regex question. by FeistyLemur

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