Perl regular expressions to capture parts of command output - regex

Question

Edited the question : I have added a third function. I have come up with a regex which seems to be correct . (1st and 2nd function work as expected. )
I have written a couple of functions which are in a library, and I call the functions from my test script. I'm having some issues with the regular expressions. Can somebody help me out with the regular expressions?
Function 1:
sub ipsec_version {
my ($self) = #_;
my $cmd = 'sudo -s ipsec version ';
my $version = 0;
#execute the command
$self->execute($cmd);
foreach my $line ( #{ $self->get_stdout() } ) {
if ( $line =~ m/strongSwan/msx ) {
$version = $1;
}
}
return $version;
}
Function call:
$self->{'ipsec_version'} = $self->{'ipsec_obj'}->ipsec_version();
INFO('[Startup] ipsec version is : ' . $self->{'ipsec_version'} );
Actual output:
Use of uninitialized value in concatenation (.) or string at ... line 37.
ipsec version is :
Expected output:
strongSwan U5.1.2/K3.16.0-30-generic
Command output:
I need the script to capture the expected output string from this
Linux strongSwan U5.1.2/K3.16.0-30-generic
Institute for Internet Technologies and Applications
University of Applied Sciences Rapperswil, Switzerland
See 'ipsec --copyright' for copyright information.
Function 2:
sub ipsec_status {
my ($self,$connection_name) = #_;
my $cmd = 'sudo -s ipsec status ' . $connection_name;
my $status = 0;
#execute the command
$self->execute($cmd);
foreach my $line ( #{ $self->get_stdout() } ) {
if ( $line =~ m/Security\sassociations\d\()/ ) {
$status = $1;
}
}
return $status;
}
Function call:
$self->{'ipsec_status'} = $self->{'ipsec_obj'}->ipsec_status('connection');
('[Startup] ipsec status is : ' . $self->{'ipsec_status'} );
Actual output:
INFO [Startup] ipsec status is : 0
Expected output:
Security Associations (1 up, 0 connecting)
Command output:
I need the script to capture the expected output string from this
Security Associations (1 up, 0 connecting):
connection[3]: ESTABLISHED 3 seconds ago, 1.1.1.19[1.1.1.19]...10.81.1.50[10.81.1.50]
connection{3}: INSTALLED, TUNNEL, ESP in UDP SPIs: cb343e86_i abf6d1f2_o
Function 3 :
sub ipsec_restart {
my ($self) = #_;
my $cmd = 'sudo -s ipsec restart';
my $restart = 0;
$self->execute($cmd);
foreach my $line ( #{ $self->get_stdout() } ) {
if ( $line =~ /(Starting strongSwan.*IPsec$)/ ) {
$restart = $1;
last;
}
}
return $restart;
}
Function call :
$self->{'ipsec_restart'} = $self->{'ipsec_obj'}->ipsec_restart();
('[Startup] ipsec restart status is : ' . $self->{'ipsec_restart'} );
Expected output : See the highlighted text below.
I checked in https://regex101.com/ . My regex seems to be correct. /(Starting strongSwan.*IPsec$)/
Starting strongSwan 5.1.2 IPsec
Actual output is : 0

Answer 1

The problem is that you're using $1 which is set only if there are captures in the regular expression that you are using. Also, you should add a last so that you don't go on searching for a matching line once you have found one. lastly, it is wrong to habitually add the /m, /s and /x modifiers to every regex match regardless of whether they make any difference, and a leading m/ is only necessary if you are using something other than the default slash delimiters.
The first function should contain
for my $line ( #{ $self->get_stdout } ) {
if ( $line =~ /(strongSwan.*\S)/i ) {
$version = $1;
last;
}
}
and the second function is similar, although it looks like you're trying to match Security associations immediately followed by a digit, which isn't what is in the text. You also have a small a instead of a capital, which is fine if you also use an /i modifier. This captures Security Associations up to and including the last closing parenthesis on the same line. Is that what you need?
for my $line ( #{ $self->get_stdout } ) {
if ( $line =~ /(Security\s+Associations.*\))/i ) {
$status = $1;
last;
}
}

Answer 2

For function 1, assuming that all that changes is the version number, we can use
m/(strongSwan.*?) Institute/ms
as the regular expression. This will match everything from strongSwan to Institute, in a non-greedy way, and store all of it except Institute in $1.
For function 2, we will use the fact that the unknown data is contained in parentheses.
m/(Security associations \(.*?\))/