unable to extract specific string in output

csj79 · 11-22-2022, 12:42 PM

Hello Everyone,

I am trying to extract a specific string (3128) from the command below. I am actually trying to extract only port number 3128 from the output. How can I proceed?

ss -tlpn | grep squid | awk '{print $4}'

Running the above command outputs *:3128

I would like to have the command only print 3128 . How do I proceed?

I am using ubuntu 22.04.

Let me know if you have any questions.

Cheers,

boughtonp · 11-22-2022, 01:03 PM

Use sub() to replace it.

You can either remove the explicit *: part, or remove "everything not a digit", like so:

Code:

awk '/squid/ {sub("\*:","",$4);print $4}'

Code:

awk '/squid/ {sub("[^0-9]*","",$4);print $4}'

note how there's a filter for squid, removing the need for grep.

csj79 · 11-23-2022, 08:43 AM

thank you for your response. I was able to find a simpler way of doing it . See below. I didn't know that grep could print exactly what you want with the -o option

ss -tlpn | grep -i squid | grep -o 3128

boughtonp · 11-23-2022, 09:04 AM

If you already know the port number then just filter ss on it directly!

Code:

ss -tlpn src :3128 or dst :3128

What precisely are you trying to achieve?

Maybe you actually just want "systemctl status squid" or "pgrep squid" ?

grail · 11-23-2022, 10:18 AM

I agree with boughtonp, if you already know all the information, what is the point?

pan64 · 11-23-2022, 10:23 AM

Code:

ss -tlpn | grep 'squid.*3128'

probably will do the same, but as it was mentioned this is not the right way to check if squid is working properly.

csj79 · 11-23-2022, 12:15 PM

thanks boughtonp . I was actually trying to see how I can extract info from a cvs like file or extract a string for the ss output and display only the port number.
during my research on it, I cam across the grep -o option and also the awk as well.

Thanks again for all you help

Turbocapitalist · 11-23-2022, 10:48 PM

CSV (aka RFC 4180) is a surprisingly complex format. There is a new version of AWK in the works which can parse it, but it may be a while off. Otherwise you're better off going with Perl or Python.

Based on the example in the manual page:

Code:

#!/usr/local/bin/perl                                                           

use Text::CSV;
use warnings;
use strict;

my @rows;

# Read/parse CSV                                                                
my $csv = Text::CSV->new ({ binary => 1, auto_diag => 1 });

open(my $fh, "<:encoding(utf8)", "test.csv")
    or die "test.csv: $!";

while (my $row = $csv->getline ($fh)) {
    # check 3rd field for a pattern
    $row->[2] =~ m/pattern/ or next;                   
    push(@rows, $row);
}

close $fh;

print join("\n", @rows), "\n";

exit(0);