How to run perl

Same as like Bash just replace last command with “perl  filename.perl”,for perl you should save your file .perl extension.

Example1 (perl subroutine):

#!/local/bin/perl
&a();
&b();
sub a
{
         print “Unix”
}
sub b
{
         print “programming”
}

Example2 (perl scalar variable / perl $ variable):

#!/local/bin/perl
print “n=$n\n”;
print “n is zero\n” if ($n==0);
if($n eq “ ”)
{
       print STDERR “This is error”;
}
$n=5;
print “n=$n\n”;

Example3 (perl vector variable):

#!/local/bin/perl
@$%
@arr[0]=”abc”;
@arr[1]=”def”;
@arr[2]=”ghi”;
print “@arr[0] @arr[1]”;
foreach $v(@arr)
{
        print $v,”\n”;
}
print “Total element $#arrr”;
for($i=0;$i<3;$i++)
{
        print @arr[$i];
}

Example4 (perl shift):

#!/local/bin/perl
@arr=”abc  def  ghi”;
$a=shift(@arr)
print $a;

Example5 (perl split):

#!/local/bin/perl
@arr2=split(“ ”,”I like programming”);
foreach $p(@arr)
{
          print $p,”\n”;
}

Example6(Associate array)

Index of array to be define by string [to run associate array “perl  perlFile.perl   myfile.txt”]

#!/local/bin/perl
$animal{“dog”}=”plays stupid”;
$animal{“penguine”}=”nice animal”;
print $animal{“dog”};

Example7 (perl open / Perl read file):

#!/local/bin/perl
open(file_handler,”textfile.txt”);
while ($line=<file_handler>)
{
        chop  $line;
        print “line=($line)\n”
}

Example8 (Two file read using file handle):

#!/local/bin/perl
open(file_handler1,”textfile.txt”)||die ”can’t open\n”;
open(file_handler2,”textfile2.txt”) ||die ”can’t open\n”;
while (($line1=<file_handler1>)||($line2=<file_handler2>))
{
          chop  $line1;
          chop  $line2;
          print “$line1 $line2\n”
}

Example9 (Execute all file using perl):

#!/local/bin/perl
open(file_handler1,”@ARGV[0]”)||die ”can’t open\n”;
while (<file1>)
{
      print $_;
}

Example10 (Perl function / Perl subroutine):

#!/local/bin/perl
$a=”Silver”;
$b=”gold”;
&Print_Arg($a,$b);
sub Print_Arg
{
        ($local_a,$local_b)=@_;
         print “($local_a,$local_b \n”;
}

Example11 (Perl retrieve file information):

#!/local/bin/perl
@arr=stat(“file.txt”);
($a,$b,$c)=stat(“file.txt”);                 //$a=device $b=inode $c=permission
$mask=020;
if($c & $mask)
{
          print “File is writable by graph\n”;
}

Example12(Perl replace existing text file’s text)

#!/local/bin/perl
$out=”temp.txt”;
Unlink $out;
print “Enter the string you want to find:\n\n”;
$find=<STDIN>;
chop  $find;
print “Enter string you want to replace:\n\n”
$replace=<STDIN>;
chop $replace;
print  “\n Find: $find\n”;
print  “\n Replace: $replace\n”;
print “\n Confirm(Y/n)”;
$a=<STDIN>;
if($a!=”Y”)
{
        Die “Aborted \n”;
}
else
{
        print “Type ctl+c to Enter \n”;
}
Open(Input,”Unix”)||die  “Couldn’t open the file\n”;
Open(Output,”>$out”)||die “Couldn’t open the file\n”;
while(<Input>)
{
        S/$find/$replace/g;
        print output;
}
close(output);

Cshell

Run cshell same as like bash

Example1 (tcsh Array):

#!/bin/tcsh
Set   arr=(10 20 30)
echo  $arr[3]
echo  $#arr
echo  $arr[$#arr]

Example2 (tcsh switch):

#!/bin/tcsh
if(-f  $argv[2]) then
echo  “File exist.copy anyway?”
switch($<)
case y:
                break sw
default:
                echo  “Do nothing”
end sw
end if
echo  –n  “copying $argv[1] to $argv[2]”
cp $argv[1] $argv[2]
echo done