How to iterate or loop through all elements of an array in a perl script

Here you can see multiple ways of implementing array iterator.

Example1:

This example reads each element of the array to a variable “$item” in a loop.

@myarray = ('One', 'Two', 'Three');
foreach $item (@myarray) {
  print $item;
}

Example2:

This example avoids intermediate variable “$item” shown in the above script. However if you have nested loops, this method is not suitable. Each element is available in a special variable “$_” inside the loop.

@myarray = ('One', 'Two', 'Three');
foreach (@myarray) {
  print $_;
}

Example3:

This example is similar to “for” loop style of a C programmer .

@myarray = ('One', 'Two', 'Three');
for($i=0; $i <= $#myarray; More >

How to pass and read function or subroutine arguments in a perl script

All the arguments passed to a perl subroutine are packed in an array “@_”. The following script shows you how to access function arguments in a subroutine.

[nick@techpulp ~]# cat funargs.pl
#!/usr/bin/perl

sub myfun
{
  my $i = 0;
  $nargs = $#_+1;
  print "Number of arguments: $nargs\n";
  foreach $arg (@_) {
    $i++;
    print "Arg $i: $arg\n";
  }
}

myfun("One", "Two");
[nick@techpulp ~]#

Let us run the above script.

[nick@techpulp ~]# ./funargs.pl
Number of arguments: 2
Arg 1: One
Arg 2: Two
[nick@techpulp ~]#

If the subroutine is expected to take fixed number of arguments, you can simplify the script as following.

[nick@techpulp ~]# More >

How to read input line by line in a perl script

The following perl script reads one line at a time from the standard input which can be from normal console or a redirected file using pipes.

[nick@techpulp ~]# cat readline.pl
#!/usr/bin/perl

$line = 0;
while (<>) {
  $line++;
  print "Line $line: " . $_;
}
[nick@techpulp ~]# chmod +x readline.pl
[nick@techpulp ~]#

In the above script, The “<>” reads a line from standard input file of the script and “$_” contains the last read data.

For input, let us consider following file (input.txt) which contains four lines.

[nick@techpulp ~]# cat input.txt
first line
second line
third line
fourth line
[nick@techpulp ~]#

Now let More >

How to read or access command line arguments in a perl script

All command line arguments passed to a perl script are stored in a array named @ARGV. So $ARGV[0] contains first argument, $ARGV[1] contains second argument and so on. As all command line arguments are packed in an array, you can use $#ARGV to get the index of last element. That means ($#ARGV+1) will give you number command line arguments passed to the script.

Look at the following example, that iterates through all command line arguments passed.

[nick@techpulp ~]# cat cmline.pl
#!/usr/bin/perl

$nargs = $#ARGV + 1;
print "you have passed $nargs command line arguments\n";

for($i=0;$i<$nargs;$i++) {
   print "Arg $i: $ARGV[$i]\n";
}
[nick@techpulp More >

How to reset WordPress adminstrator’s password using phpMyAdmin

Its is recommended that this method of setting password is used only as last resort. Because there is a standard way of resetting password using “Lost your password?” option by which you get a mail containing newly generated random password.

WordPress saves MD5 hash of plain passwords. For thos who don’t know what is MD5, it is a digest algorithm (cryptography) that generates fixed length digest for a variable length input. So you will not see plain passwords in WordPress database. This feature ensures even the administrator user unable to know the passwords of subscribed users.

Follow the instruction given below to More >

How to include a CSS stylesheet in another style sheet – Use import url statement

You can use “import url(..)” statement to include a CSS file with in an another. For example, you can include another css file (file2.css) in a style sheet file file1.css by placing following statement in file1.css.

@import url(file2.css);

The above url is relative and file2.css is expected to be available at the same directory level as file1.css.

Otherwise you can specify a complete URL or a relative URL as shown in the following examples.

Import from a directory with absolute path on the same server:

@import url(/css/file2.css);

Import from a directory with relative path on the same server:

@import url(../css2/file2.css);

Import from another server using More >

How to set various colors for A links using CSS

The CSS supports following for <A> tag.

Name Description a:link Style is applied to all non-visited links a:visited Style is applied to all visited links a:hover Style is applied when mouse moves over a link a:active Style is applied to active links. A link becomes active when it is clicked

It is always recommended to specify the styles for a link in the same order as specified in the above table.

An example style specification:

<style type="text/css">
a:link {
  color: #ff0000;
  background-color: #00ffff;
  text-decoration: none
}

a:visited {
  color: #00ff00;
  background-color: #ff00ff;
  text-decoration: none
}

a:active {
  color: #0000ff;
  background-color: #ffff00;
  text-decoration: none More >

How to scroll backwards on text-mode console or graphical terminal to see history of my previous activity

If you are using text-mode console, you can use key combination “Shift+PageUp” to scroll up by one page. Similarly use key combination “Shift+PageDown” to scoll down by a page in console history. You need to use regular “Page Up” and “Page Down” keys and the keys on numeric keypad do not work.

Generally, the same key combinations work in graphical terminal programs like xterm, GNOME Terminal and Konsole etc. The KDE desktop based terminal program konsole adds more flexibility by supporting “Shift+Up” and “Shift+Down” key combinations to scroll down and up by a line in history. This is more convinient in More >

What is the latest version of Linux kernel and where do I get it

If you are a regular user, it is recommended to use updates provided by the Linux distribution you are using. It is easier and convinient way of upgrading to the latest version of kernel. All modern Linux distributions come with an automatic updater that makes the job easy and it ensures that your system is not broken.

However if you are looking to compile your own kernel, you can visit http://www.kernel.org/ web site that provides sources of all versions of Linux kernels including the latest production and development kernels versions. Typically you would see the current stable kernel mentioned on the More >