Shell Programming and Scripting

Hi All
I have searches getopts function in Perl a lot, but yet i didn't cleared with it.

First I want to know what is the meaning of
getopts('t:c:', \%options);

and please explain getopts function in an easy way..

Is this homework?

The Getopt::Std module comes with sufficient documentation, try perldoc Getopt::Std and be clear about what you do not follow in the documentation if you need further explanation.

no, I am learner of Perl

Code:

getopts('t:c:', \%options);

Is a call to the getopts function, it expects there to be 2 flags (-t and -c) each of these require a para;
meter the values of which will be accessable in the %options hash. So if the Perl script is called as follows my_script.pl -t 5 -c apples then within the scope that %options is defined the values can be accessed as $options{t} and $options{c}. Seriously read perldoc Getopt::Std

'getopts' function from Getopt::Std module would allow you to provide command line options and values to those options.

A simple example.. in echo "hello" | cut -c1 , -c is an option provided to cut and 1 is a value quantifying that option. In this case you're telling cut command to cut string character-wise and specifically just the 1st character.

Here's a sample perl program illustrating the use of getopts:

Code:

#! /usr/bin/perl
use warnings;
use strict;
use Getopt::Std;

my %options;
getopts ("t:c:", \%options);

foreach (keys %options) {
    print "Option '$_' ; Value '$options{$_}'\n";
}

Code:

$ ./test.pl -t hello -c world
Option 'c' ; Value 'world'
Option 't' ; Value 'hello'

The colon in "t:c:" tells 'getopts' that 't' and 'c' options need to have values along with them. If values are not supplied, then the hash %options would have a key as 't' with a null value. This is of no use, right.

You could also give getopts ("tc", \%options) to tell getopts that along with options 't' and 'c', values would not be supplied. In this case, the corresponding values for keys 't' and 'c' in hash %options would be 1.

You should consider Skrynesaver's advice: Seriously read perldoc Getopt::Std