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splitting the scalar variables in an array

by sunil9009 (Acolyte)
on Nov 16, 2013 at 05:17 UTC ( #1062852=perlquestion: print w/ replies, xml ) Need Help??
sunil9009 has asked for the wisdom of the Perl Monks concerning the following question:

I have a list of hostclasses each having a list of host, I want to combine all the hosts in the hostclasses to give me an array of hosts. Command "expand-hostclass" gives me a list of hosts with each host as a newline. My problem is that the array considers hosts in each hostclass as a scalar ($hosts_per_hostclass).I want to flatten the scalar ($hosts_per_hostclass) to an array, so that each element in the array is a hostname. Hope I am not confusing too much Please help. I tried the following code

#!/usr/bin/perl my @hostclass = ('Hostclass-A','Hostclass-B','Hostclass-C'); my @hosts; my @TotalHosts; my $class; my $hosts_per_hostclass; gethosts(); sub gethosts { foreach $class(@hostclass) { $hosts_per_hostclass = `expand-hostclass` ; push (@TotalHosts,$hosts_per_hostclass); my @dd = split "\n", @TotalHosts; print "@dd \n"; } }

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Re: splitting the scalar variables in an array
by Athanasius (Monsignor) on Nov 16, 2013 at 06:55 UTC

    split expects its second argument to be a string (i.e., a scalar), so using the array @TotalHosts here puts the array into scalar context, and split gets the number of elements in the array. You need to change this line:

    my @dd = split "\n", @TotalHosts;

    to something like this:

    my @dd; push @dd, split "\n", $_ for @TotalHosts;

    which calls split on each element of the array in turn. This works provided that each of the array elements is a string.

    Hope that helps,

    Athanasius <°(((><contra mundum Iustus alius egestas vitae, eros Piratica,

      my @dd; push @dd, split "\n", $_ for @TotalHosts;

      No need for push and for:

      my @dd=map { split "\n" } @TotalHosts;

      Alexander

      --
      Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)

      Thanks for the help, I modified the code but that didnt helped either. The scalar value for @dd returned by the code is as follows 1 1 4 Thats because Hostclass-A has 1 host, Hostclass B has 1 and C has 4 hosts. I want scalar(@dd) to be just 6 ( each host should be a separate element in an array )

      sub gethosts { foreach $class(@hostclass) { chomp (@hosts_per_hostclass = `/opt/systems/bin/expand-hostclass --hos +ts -r $class`) ; my @dd; push @dd, split "\n", $_ for @hosts_per_hostclass; print scalar(@dd) , "\n"; } }

        Consider this resolved, foreach was printing it 3 times. Final working code is as follows. Thanks to all of you guys fo the pointers.

        sub gethosts { foreach $class(@hostclass) { chomp (@hosts_per_hostclass = `/opt/systems/bin/expand-hostclass --hos +ts -r $class`) ; #print "@hosts_per_hostclass \n"; push @dd, split "\n", $_ for @hosts_per_hostclass; } return @dd; }
Re: splitting the scalar variables in an array
by soonix (Deacon) on Nov 16, 2013 at 08:14 UTC
    I would move the split and print out of the loop.
    Update: wasn't yet awake... push @TotalHosts, split ... IN the loop, and print, of course, after the loop.
Re: splitting the scalar variables in an array
by jwkrahn (Monsignor) on Nov 16, 2013 at 10:36 UTC
    $hosts_per_hostclass = `/opt/systems/bin/expand-hostclass --hosts -r $ +class` ; push (@TotalHosts,$hosts_per_hostclass);

    Back-quotes in list context return a list so you could do this:

    chomp( @hosts_per_hostclass = `/opt/systems/bin/expand-hostclass --hos +ts -r $class` ); push @TotalHosts, @hosts_per_hostclass;

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