Neo
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Posts by Neo
How to configure apache virtual host in Microsoft Windows for safer development
Jan 6th
Typically for web development, one likes to simulate the web environment by using actual domain name as is instead of using some local IP address. It is very useful in case if you want to host WordPress and would like to copy your version of database as is from development server to the the actual hosting server. The applications like WordPress store domain names in the database while storing your posts as part of permalinks etc.
Another use for having real simulated environment is to ensure your ad slots like Google AdSense, DoubleClick etc appear without any issues. Otherwise the ads More >
How to do search and replace operation on a portion of a string in perl
Dec 24th
I recommend reading this article to know more about usage of substr function in perl. Basically substr function and a typical search and replace mechanism (s///g) can be combined to achieve the goal in a single statement.
Look at the following script which replaces the word “goes” to “moves” in first first 10 characters of a string variable “$str”.
#!/usr/bin/perl $str="What goes around comes around"; print $str . "\n"; substr($str,0,10) =~ s/goes/moves/g; print $str . "\n";
Output of the above script is as follows:
[neo@techpulp ~]# perl replsubstr.pl What goes around comes around What moves around comes around [neo@techpulp ~]#
You can play with More >
How to get substring in perl – substr function
Dec 23rd
In perl, the substr function can be used to access individual characters or a portion of a string. The syntax of substr function is as follows:
substr ( string, offset [, count] )
Arguments:
- string – string from which you would like to extract a sub-string
- offset – this indicates start of the sub-string you want to extract
- count – length of the sub-string to extract
A negative number also can be specified for “offset” argument that make substr to count the characters in the reverse direction (i.e from the end). If “0″ is specified as offset, sub-string is extracted from beginning of the string. If a positive More >
How to check if bash variable is a number or not
Dec 20th
The following example illustrates the simplest way to check if a variable is holding an number or not. Consider the following scripts which checks the first command line argument and tells us if it is a number or not.
[neo@techpulp ~]# cat numcheck.sh #!/bin/bash if [ "$1" -eq "$1" >& /dev/null ]; then echo "'$1' is an integer" else echo "'$1' is not an integer" fi [neo@techpulp ~]#
Basic logic behind this is to use the variable in an integer expression and find the result of the operation. Let run the above script with different arguments.
[neo@techpulp ~]# ./numcheck.sh 123 '123' is More >
How to iterate or loop through all elements of an array in a perl script
Dec 18th
Here you can see multiple ways of implementing array iterator.
Example1:
This example reads each element of the array to a variable “$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
Dec 17th
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
Dec 16th
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 reset WordPress adminstrator’s password using phpMyAdmin
Dec 13th
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 set various colors for A links using CSS
Dec 9th
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 clickedIt 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
Dec 5th
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 >
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