How could you check the existence of a function (say new) within a package (say CGI) in Perl?

use CGI;

$cgi=CGI->new;

if (exists &CGI::new)
{
    print "Exists\n";
}

Or

if ( defined( &CGI::new ) )
{
print "Defined\n";
}

Or

if ( CGI->can('new') )
{
print "Exists\n";
}

Or

if ( $cgi->can('new') )
{
print "Defined\n";
}

How could you list out all the variables defined in a package in Perl?

use CGI;

no strict 'refs';

foreach ( keys %CGI:: )
{
print "$_\n";
}

How could you list all the methods defined in the package (say CGI) in Perl?

use CGI;

no strict 'refs';
print join ', ', grep { defined &{ "CGI::$_" } } keys %{ CGI:: };

When is “use lib” implemented in Perl?

‘use lib’ is used in two cases:

• When you have a fixed, but not standard company-wide environment in which you put modules in a common standard location.
• When you are developing an application and you'd like to make sure the script always picks up the modules relative to their own location.

How could you disable strict for a block of code in Perl?

It can be disabled with "no strict".

#!/usr/bin/perl
use strict;
 
my $me=$0;
print "$me\n";
 
open (FH, "< $0") or die "$!";  
while (<FH>)
{
no strict;
  $count=0;  
print "$_" . ++$count;
}

How could you extract range of characters in a fixed string in UNIX?

echo "Hello World!" | cut -c 3-7

How could you check the success of opening a file in Perl?

open ( FILE, "$0" );

if ( tell ( FILE ) == -1 )
{
        print "Not Opened!";
}

close ( FILE );

How could you execute command stored in a string or variable in Shell Scripting?

#!/bin/bash

CMD="ls -lrt"
eval $CMD

How could you run commands/scripts when you log out session in UNIX?

Run commands/scripts when you log out by appending required lines to the ".logout" file in your HOME directory.

sh shell : ~/.sh_logout
bash shell : ~/.bash_logout
ksh shell : ~/.ksh_logout
tcsh / csh : ~/.logout

Next add the below line to your ".profile" file :
trap '. $HOME/.sh_logout; exit' 0

How could you generate a sequence of numbers in Shell Scripting?

#!/bin/bash

for (( count=1; count <= 3 ; count++ ))
do
 echo "Value of count = $count."
done

# Or

#!/bin/bash

for count in $(seq 4 7)
do
 echo "Value of count = $count."
done

# Or

#!/bin/bash

for count in {7..10}; do
 echo "Value of count = $count."
done