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Old 04-25-2013, 08:47 AM   #1
Regnets1
LQ Newbie
 
Registered: Feb 2012
Posts: 24

Rep: Reputation: Disabled
assign the contents of an array to a new variable in perl


I am writing one of my first perl scripts and I need to create a new variable with the elements of an array. I need to take an IP address entered by a user and manipulate the last octet so it can be used in a router configuration. I am able to split the address into it's four octets. I can also make changes to the array elements as needed, but I can not reassemble the new address after I manipulate the octet I want. Here is my sample code:
Code:
#!/usr/bin/perl
# tests the use of ipcalc function in linux with matching
use strict;
use warnings;

my $ip_addr;
my $net;
my $mask;
my $cidr;
my $pe;
my $ce;
#my $nw_addr;
print "Enter IP address: e.g. 1.1.1.1/32\n";
$ip_addr = <>;
my @ipc_arr=`ipcalc -n -m -b -p $ip_addr`;
        for(@ipc_arr){
        chomp;
        print $_ . "\n";
        }
print "\n";
($net) = $ipc_arr[3] =~ m/=(.+)/;
print "The network is $net \n";
($mask) = $ipc_arr[0] =~ /=(.+)/;
print "\n";
print "The Subnet mask is $mask \n";
print "\n";
($cidr) = $ipc_arr[1] =~ /=(.+)/;
print "The CIDR notation is /$cidr \n";
print "\n";
print "You entered $net/$cidr which equals $net $mask\n";
#my @pe_arr = $net =~ /\.(\d+)$/ ; #only grabs last octet.
#my @pe_arr = $net =~ /(^\d+)\.(\d+)/ ; # returns first two octets

my @pe_arr = $net =~ /(^\d+)\.(\d+)\.(\d+)\.(\d+)/ ; # grabs all 4 octets!!!!!!!
        for (@pe_arr){
        print $_ . "\n";
        ($pe) = $pe_arr[3];
        $pe = ($pe + 1);
        chomp ($pe);
        #my ($nw_addr) = ($pe_arr[0]"."$pe_arr[1]"."$pe_arr[2]"."$pe); #doesn't work
        }
print "the last octect is $pe on the PE \n";
print "\n";
my ($nw_addr) = $pe_arr[0].$pe_arr[1].$pe_arr[2].$pe; #doesn't work
print"\n";
print $nw_addr "\n";
print "\n";
which yields the output:

Code:
Enter IP address: e.g. 1.1.1.1/32
67.54.99.136/29
NETMASK=255.255.255.248
PREFIX=29
BROADCAST=67.54.99.143
NETWORK=67.54.99.136

The network is 67.54.99.136 

The Subnet mask is 255.255.255.248 

The CIDR notation is /29 

You entered 67.54.99.136/29 which equals 67.54.99.136 255.255.255.248
67
54
99
136
the last octect is 137 on the PE 


Can't use string ("675499137") as a symbol ref while "strict refs" in use at ./ipcalc_test.pl line 47, <> line 1.
So, how can I assign $nw_addr with some of the first three elements of @pe_arr and the variable $pe? Additionally I get errors trying to add in the periods between the octets. The script fails and tells me "Scalar found where operator expected at...."
I have tried all kinds of combinations, but can not get the script to work.
Any help is appreciated.

thanks,
Robert
 
Old 04-25-2013, 09:42 AM   #2
grail
LQ Guru
 
Registered: Sep 2009
Location: Perth
Distribution: Manjaro
Posts: 9,252

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So not being a Perlite, is there no join command in Perl? (seems unlikely)

As for your example, the long way would be:
Code:
my $nw_addr = "$pe_arr[0].$pe_arr[1].$pe_arr[2].$pe";
As you can see, you still need to tell print that dot is a string (or at least this works for me )

Last edited by grail; 04-25-2013 at 09:43 AM.
 
Old 04-25-2013, 11:04 AM   #3
Regnets1
LQ Newbie
 
Registered: Feb 2012
Posts: 24

Original Poster
Rep: Reputation: Disabled
Thanks very much Grail! After all the different combinations I tried, I can't believe I didn't run up against that one. So double quoting the variable definition allows me to create the $nw_addr. And I found if I put parenthesis around $nw_addr, I can print it.

Code:
my $nw_addr = "$pe_arr[0].$pe_arr[1].$pe_arr[2].$pe";
print"\n";
print ($nw_addr);
print "\n";
Thanks For your help! my proof of concept is working as expected now. Funny how "Working script" cures a headache faster than any pill can

here's the output I get now :
Code:
Enter IP address: e.g. 1.1.1.1/32
67.54.99.136/29
NETMASK=255.255.255.248
PREFIX=29
BROADCAST=67.54.99.143
NETWORK=67.54.99.136

The network is 67.54.99.136 

The Subnet mask is 255.255.255.248 

The CIDR notation is /29 

You entered 67.54.99.136/29 which equals 67.54.99.136 255.255.255.248
67
54
99
136
the last octect is 137 on the PE 


67.54.99.137
 
Old 04-25-2013, 12:02 PM   #4
grail
LQ Guru
 
Registered: Sep 2009
Location: Perth
Distribution: Manjaro
Posts: 9,252

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I am not sure why you need the brackets ... should be able to print without them. Also, you can append your newline to your print statement to with a comma:
Code:
print $nw_addr,"\n";
Maybe one of the Perl gurus will tell you if it is better practice to include the brackets or not?
 
Old 04-25-2013, 03:57 PM   #5
David the H.
Bash Guru
 
Registered: Jun 2004
Location: Osaka, Japan
Distribution: Debian sid + kde 3.5 & 4.4
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I could hardly even be called a beginner at perl, but 30 seconds on google determined that it does indeed have a join function.

http://www.misc-perl-info.com/perl-join.html

Code:
my $string = '123.456.789.012/32' ;

my @array = split( /[.\/]/ , $string ) ;

$array[3] = "876" ;

$string = join( "." , @array[0..3] ) ;

$string = $string . "/" . $array[4] ;

print $string , "\n" ;
I got the above working in a quick test. Output: "123.456.789.876/32"

Last edited by David the H.; 04-25-2013 at 03:59 PM. Reason: small code cleanup
 
  


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