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Full Discussion: Getopt Help
Top Forums Shell Programming and Scripting Getopt Help Post 303015612 by mutley2202 on Sunday 8th of April 2018 02:50:38 PM
Old 04-08-2018
Getopt Help

Hi All,

An old work friend wrote a script which I've been trying to understand how a section of it currently works and work out how i can add some command line switches which i can use later in the script to append the output depending on the command line arguements.

Currently it works by triggering is as per the below

Code:
./data_parser.pl -f testinputfile.txt

Code:
use strict;
use Getopt::Std;
use constant DEBUG => 0;

$| = 1;
my $current_colour = '36';

my %opt = ('f' => '-');

getopts("f:", \%opt);
my $opentag = $opt{'f'};
if ($opt{'f'} eq '-') {
        ;
} elsif (-f $opt{'f'}) {
        if ($opt{'f'} =~ /\.gz$/) {
                $opentag = 'gunzip -c '.$opt{'f'}.'|';
        }
} else {
        die "File ", $opt{'f'}, " not found\n";
}
open (FH, $opentag);

I dont understand what the getopts parts are doing, would someone be kind enough to shed some light and point me in the right direction with how i can add some switches on command execution.

Thanks in advance.
 

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Getopt::Std(3pm)					 Perl Programmers Reference Guide					  Getopt::Std(3pm)

NAME
getopt, getopts - Process single-character switches with switch clustering SYNOPSIS
use Getopt::Std; getopt('oDI'); # -o, -D & -I take arg. Sets $opt_* as a side effect. getopt('oDI', \%opts); # -o, -D & -I take arg. Values in %opts getopts('oif:'); # -o & -i are boolean flags, -f takes an argument # Sets $opt_* as a side effect. getopts('oif:', \%opts); # options as above. Values in %opts DESCRIPTION
The getopt() function processes single-character switches with switch clustering. Pass one argument which is a string containing all switches that take an argument. For each switch found, sets $opt_x (where x is the switch name) to the value of the argument if an argument is expected, or 1 otherwise. Switches which take an argument don't care whether there is a space between the switch and the argument. The getopts() function is similar, but you should pass to it the list of all switches to be recognized. If unspecified switches are found on the command-line, the user will be warned that an unknown option was given. The getopts() function returns true unless an invalid option was found. Note that, if your code is running under the recommended "use strict 'vars'" pragma, you will need to declare these package variables with "our": our($opt_x, $opt_y); For those of you who don't like additional global variables being created, getopt() and getopts() will also accept a hash reference as an optional second argument. Hash keys will be x (where x is the switch name) with key values the value of the argument or 1 if no argument is specified. To allow programs to process arguments that look like switches, but aren't, both functions will stop processing switches when they see the argument "--". The "--" will be removed from @ARGV. "--help" and "--version" If "-" is not a recognized switch letter, getopts() supports arguments "--help" and "--version". If "main::HELP_MESSAGE()" and/or "main::VERSION_MESSAGE()" are defined, they are called; the arguments are the output file handle, the name of option-processing package, its version, and the switches string. If the subroutines are not defined, an attempt is made to generate intelligent messages; for best results, define $main::VERSION. If embedded documentation (in pod format, see perlpod) is detected in the script, "--help" will also show how to access the documentation. Note that due to excessive paranoia, if $Getopt::Std::STANDARD_HELP_VERSION isn't true (the default is false), then the messages are printed on STDERR, and the processing continues after the messages are printed. This being the opposite of the standard-conforming behaviour, it is strongly recommended to set $Getopt::Std::STANDARD_HELP_VERSION to true. One can change the output file handle of the messages by setting $Getopt::Std::OUTPUT_HELP_VERSION. One can print the messages of "--help" (without the "Usage:" line) and "--version" by calling functions help_mess() and version_mess() with the switches string as an argument. perl v5.18.2 2014-01-06 Getopt::Std(3pm)
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