act on a file list

perl197 has asked for the wisdom of the Perl Monks concerning the following question:

I'm trying to coble the code example below to perform work on the file name in the list. I have code that will pgp a single passed file name but I would like to loop through a file list and perform the same process against each filename in the list. How can i incorporate the $cmd component with the loop example such that each file_name in the list can be acted up on? I.e., i've tried substituting the print request with the cmd command but there's something fundamental i'm missing with this attempt

#code snippet that works in another script:
$cmd = "gpg --recipient $gpg_key -q --yes -e $directory/$file_name";
$rc = system($cmd);

#code loop example i'm having trouble combining with 

#!/usr/bin/perl -w
use strict;

my $file = "junk";
open (FH, "< $file") or die "Can't open $file for read: $!";
my @file_name;
while (<FH>) {
    push (@file_name, $_);
}
close FH or die "Cannot close $file: $!";

print @file_name;    # see if it worked
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Re: act on a file list
by Athanasius (Archbishop) on Jun 30, 2014 at 15:30 UTC

Hello perl197, and welcome to the Monastery!

Just a side note. The code:

my @file_name;
while (<FH>) {
    push (@file_name, $_);
}
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can be replaced with the simpler and more idiomatic:

my @file_name = <FH>;
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Here is the explanation, from readline:

In scalar context, each call reads and returns the next line until end-of-file is reached, whereupon the subsequent call returns undef. In list context, reads until end-of-file is reached and returns a list of lines.

In your code, while (<FH>) puts <FH> into scalar context¹, so the while loop is needed to call <FH> repeatedly until the file is exhausted. But in the simpler version, assignment to an array variable (in this case, @file_name) puts the call to <FH> into list context, so <FH> is called only once and returns a list of all the lines in the file.

Hope this is of interest,

Update: ¹Because of the implicit assignment to $_.

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

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Re: act on a file list
by toolic (Bishop) on Jun 30, 2014 at 15:05 UTC

for (@file_name) {
    chomp;
    my $cmd = "gpg --recipient $gpg_key -q --yes -e $directory/$_";
    my $rc = system($cmd);
}
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