April 16, 2012

Perl Code Snippets

By Mohammed Abualrob Code Snippets 0 Comments

Perl Search for Files and Directories

# Use the file module to find files
use File::Find;	

# Current file can be accessed by $File::Find::name
# Inside the sub you can apply any command for example
# changing the file mode to 777
find (sub { system("chmod 777 $File::Find::name"); },"/some/path");

# Use the file module to find files

use File::Find;

# Current file can be accessed by $File::Find::name

# Inside the sub you can apply any command for example

# changing the file mode to 777

find (sub { system("chmod 777 $File::Find::name"); },"/some/path");

Perl Remove Directory

# Use the file module
use File::Path;

# Remove the entire directory
rmtree ("/some/path");

# Use the file module

use File::Path;

# Remove the entire directory

rmtree ("/some/path");

Perl Extract File and Directory Names from Full Paths

# Use the file module
use File::Basename;

# Extract base name
$filename = basename ("/some/path");

# Extract directory name
$dir = dirname ("some file name");

# Use the file module

use File::Basename;

# Extract base name

$filename = basename ("/some/path");

# Extract directory name

$dir = dirname ("some file name");

Perl Copy File

# Use file module
use File::Copy;

# Copy files
copy("file1", "file2") or 
die "Copy failed: $!";

# Move files
move("/dev1/fileA", "/dev2/fileB");

# Use file module

use File::Copy;

# Copy files

copy("file1", "file2") or

die "Copy failed: $!";

# Move files

move("/dev1/fileA", "/dev2/fileB");

Perl Command Line Options

# Use Getopt module
use Getopt::Long;

# In the example below
# (a) and (g) do not take values
# (gr) and (gc) take values
# if the command option (a) is used then $add is 1
# If the (gr) command option is used with some value
# then the $getrel variable will hold that value
# It is up to the programmer to choose the names
# for the command options and the variable names
# that hold their values
$result = GetOptions
(
  	"a"      => \$add,
  	"g"      => \$get,
  	"gr=f"   => \$getrel,
  	"gc=f"   => \$getcase,
);

# If $result is not 1 then command options 
# were not used properly
if ($result != 1)
{
	# Print usage
}

# Use Getopt module

use Getopt::Long;

# In the example below

# (a) and (g) do not take values

# (gr) and (gc) take values

# if the command option (a) is used then $add is 1

# If the (gr) command option is used with some value

# then the $getrel variable will hold that value

# It is up to the programmer to choose the names

# for the command options and the variable names

# that hold their values

$result = GetOptions

(

"a" => \$add,

"g" => \$get,

"gr=f" => \$getrel,

"gc=f" => \$getcase,

);

# If $result is not 1 then command options

# were not used properly

if ($result != 1)

{

# Print usage

}

Perl Environment Variables

# Environment variables are accessed as follows
$ENV{env_name};

1 2	# Environment variables are accessed as follows $ENV{env_name};

Perl Check File Exists

if (-f file_name)
{
   # Do something
}

if (-f file_name)

{

# Do something

}

Perl Get User Input

chomp ($userInput = );

1	chomp ($userInput = );

Perl Upper Case

$uc_string = uc ($sc_string);

1	$uc_string = uc ($sc_string);

Perl String Comparison

if ($userInput eq "Y")  # u can use ne

1	if ($userInput eq "Y") # u can use ne

Perl Exit Error

die "Error: $!\\n";

1	die "Error: $!\\n";

Perl Get Number of Lines of an Array

my $numberLines = $#Array + 1;

1	my $numberLines = $#Array + 1;

Perl Change Directory

chdir ($dir) or  
die "Error : can not cd to [ $dir ] : $!\\n";

1 2	chdir ($dir) or die "Error : can not cd to [ $dir ] : $!\\n";

Perl Number Comparison

if ($num1 == $num2)
{
    # Do something
}

if ($num1 == $num2)

{

# Do something

}

Perl Delete File

unlink <$file_name> or 
die "Error : can not delete [ $file_name ] for reading : $!\\n";

1 2	unlink <$file_name> or die "Error : can not delete [ $file_name ] for reading : $!\\n";

Perl Delete List of Files

unlink (*);

1	unlink (*);

Perl Read a List of Files and Directory Names

my @filesArr = </some/path>;

1	my @filesArr = </some/path>;

Perl For Loop

for ($t = $from; $t <= $to; $t++)
{
    # Do something
}

for ($t = $from; $t <= $to; $t++)

{

# Do something

}

Perl Foreach

foreach (@array)
{
	# current entry found in $_
}

foreach (@array)

{

# current entry found in $_

}

Perl Search for a Pattern in an Array

my @keyWords = grep (/%.%/, @array);

1	my @keyWords = grep (/%.%/, @array);

Perl Directory Exists

if (-d $dir)
{
    # Do something
}

if (-d $dir)

{

# Do something

}

Perl Sort Array

foreach $x (sort @array);
foreach $x (reverse sort @array);

1 2	foreach $x (sort @array); foreach $x (reverse sort @array);

Perl Print Formatted Text

printf("%-30.30s   %-15.15s   %-10.10s\n",   "Database", "Owner", "Created On");

1	printf("%-30.30s %-15.15s %-10.10s\n", "Database", "Owner", "Created On");

Perl Create Directory

mkdir ("SCCS", 0755) or
die "doAdd: Error : can not mkdir SCCS : $!\n";

1 2	mkdir ("SCCS", 0755) or die "doAdd: Error : can not mkdir SCCS : $!\n";

Perl Replace Text Remove White Space

$var =~ s/^\s+//;
$var =~ s/\s+$//;

1 2	$var =~ s/^\s+//; $var =~ s/\s+$//;

Perl Dynamically Add to an Array

push (@my_files, $my_file);

1	push (@my_files, $my_file);

Perl String Length

$length = length($str);

1	$length = length($str);

Perl File Extension Regular Expression Check

if ($fileName =~ /\.txt\b/)
{
    # Do something
}

if ($fileName =~ /\.txt\b/)

{

# Do something

}

Perl Hash Definition

my %mHash;
$mHash{$var} = $new_value;

1 2	my %mHash; $mHash{$var} = $new_value;

Perl Split String

my @SPLT = split ("_", $string);

1	my @SPLT = split ("_", $string);

Perl Hash Loop

while (($key, $val) = each (%myHash))
{
    # Do something
}

while (($key, $val) = each (%myHash))

{

# Do something

}

Perl Pass Parameters to Function

sub myFunc
{
 	my ($var1, $var2) = @_;
}

sub myFunc

{

my ($var1, $var2) = @_;

}

Perl Current Working Directory

use Cwd;
my $currDir = getcwd;

1 2	use Cwd; my $currDir = getcwd;

Perl Number of Command Line Arguments

my $numArgs = $#ARGV + 1;

1	my $numArgs = $#ARGV + 1;

Perl Split into Variables and Array

# The first 3 tokens go to the variables
# and the rest go to the array
($v1, $v2, $mm, $v3, @array) = split (" ", $string);

# The first 3 tokens go to the variables

# and the rest go to the array

($v1, $v2, $mm, $v3, @array) = split (" ", $string);

Perl Substring

my $firstChar = substr ($str, 0, 1);

1	my $firstChar = substr ($str, 0, 1);

Perl While Loop

while ($Line ne "xyz")
{
    # Do something	
}

while ($Line ne "xyz")

{

# Do something

}

Perl Remove Trailing Characters

chomp $string;

1	chomp $string;

Perl Initialize an Array

@DBS = ("$database_1", "$database_2");

1	@DBS = ("$database_1", "$database_2");

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Mohammed Abualrob

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