CODEWITHSUNDEEP
perlfile-handling
Sam
Sam

Reputation: 2331

Using a passed in variable in a perl script

I want to do something like

for i in (1..100)
do
     ./perlScript.pl
done

where perlScript.pl will open a file handle like

#!/usr/bin/perl -w
use strict;
my $file = 'info${i}.txt';
my @lines = do {
    open my $fh, '<', $file or die "Can't open $file -- $!";
    <$fh>;
};

I would just like some advice one how to access that letter I from inside the script. Even if I could pass in the txt file as a parameter and then access it like $1 or something

Thank-you

Upvotes: 1

Views: 195

Answers (1)

xxfelixxx
xxfelixxx

Reputation: 6592

You can pass command line arguments to perl, they will show up in the special array @ARGV.

Basic Command Line Argument Passing

# In bash
./perlScript.pl 123

# In perl
my ($num) = $ARGV[0];  # The first command-line parameter [ 123 ]

Many Positional Command Line Arguments

# In bash
./perlScript.pl 123 456 789 foo bar

# In perl
my ($n1,$n2,$n3,$str1,$str2) = @ARGV;  # First 5 command line arguments will be captured into variables

Many Command Line Flags

# In bash
./perlScript.pl --min=123 --mid=456 --max=789 --infile=foo --outfile=bar

# In perl
use Getopt::Long;

my ($min,$mid,$max,$infile,$outfile,$verbose);
GetOptions(
    "min=i"     => \$min,     # numeric
    "mid=i"     => \$mid,     # numeric
    "max=i"     => \$mix,     # numeric
    "infile=s"  => \$infile,  # string
    "outfile=s" => \$outfile, # string
    "verbose"   => \$verbose, # flag
) or die("Error in command line arguments\n");

Environmental Variables

# In bash
FOO=123 BAR=456 ./perlScript.pl 789

# In perl
my ($foo) = $ENV{ FOO } || 0;
my ($bar) = $ENV{ BAR } || 0;

my ($baz) = $ARGV[0]    || 0;

perldoc perlvar - details about @ARGV and %ENV

perldoc Getopt::Long

Upvotes: 5

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