@ Regular Expression

siddheshsawant has asked for the wisdom of the Perl Monks concerning the following question:

Hello Monks,

I was working on regex in perl and I am stuck at one problem. The code that I wrote is as follows:

#!/usr/bin/perl -w
use strict;
my $str = "TEST_ENVIRONMENT    OS_NAME=AIX    BUILD_TYPE=    KERNEL_BI
+TNESS=64    USER_BITNESS=32    OS_RELEASE=6.1.0.0    CPU_CLASS=powerp
+c    MACHINE_CLASS=IBM,8203-E4A    HOSTNAME=lcla114    NUM_CPUS=5    
+CUSTOM=    ";
my $machine_class = ($str =~ /MACHINE_CLASS=\s*(\w*)/);
print "MACHINE CLASS=$machine_class";
[download]

As a output of above code I am not getting IBM . Instead, I am getting number 1. So where I am doing mistake? I want to match the string and extract the required value and then have to store that value in the variable and print it.

If anybody knows where I am doing that mistake then let me know about.Thanks in advance !!!!!

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Re: Regular Expression by ikegami (Patriarch) on May 14, 2010 at 15:15 UTC
Change `my $machine_class` to `my ($machine_class)` to cause the match to be evaluated in list context.	[reply] [d/l] [select]
Re^2: @ Regular Expression by siddheshsawant (Sexton) on May 14, 2010 at 15:29 UTC
Thanks a lot .....That worked for me	[reply]
Re: @ Regular Expression by kennethk (Abbot) on May 14, 2010 at 15:17 UTC
You are having issues with list vs. scalar context. When you write `my $machine_class = ($str =~ /MACHINE_CLASS=\s(\w)/);` Perl sees you are setting a scalar, and so interprets the right hand side in that context. Since the right hand side is a list, it assigns the size of the list (1) to `$machine_class`. You can put the assignment in list context by wrapping your variable in parentheses: `my ($machine_class) = ($str =~ /MACHINE_CLASS=\s(\w)/);` See Extracting matches in perlretut. You can read more about context in Perl in Context in perldata or Context tutorial from the Tutorials.	[reply] [d/l] [select]
Re: @ Regular Expression by wfsp (Abbot) on May 14, 2010 at 15:15 UTC
Nearly! Try `my ($machine_class) = $str =~ /MACHINE_CLASS=\s(\w)/;` [download]	[reply] [d/l]
Re: @ Regular Expression by marto (Cardinal) on May 14, 2010 at 15:16 UTC
Read and understand How do I compose an effective node title?. The title of this post is almost identical to your typo'd @ ergular expression to which it seems this question should be a child node.	[reply]
Re: @ Regular Expression by toolic (Bishop) on May 14, 2010 at 15:16 UTC
Evaluate in list context: `my ($machine_class) = ($str =~ /MACHINE_CLASS=\s(\w)/);` [download]	[reply] [d/l]