Finding Best Linux Distribution

We can find ranking of Linux distributions (distros) at site distrowatch.com. This ranking is based on Page Hits Per Day.In order to find best Linux distro, I have written a Perl script:

#!/usr/bin/perl -w
#===============================================================================
#
#         FILE:  best_distro.pl
#
#        USAGE:  ./best_distro.pl 
#
#  DESCRIPTION:  Finds best distro from distrowatch.com
#
#      OPTIONS:  ---
# REQUIREMENTS:  ---
#         BUGS:  ---
#        NOTES:  ---
#       AUTHOR:  Mitesh Singh Jat (mitesh)
#      VERSION:  1.0
#      CREATED:  Tuesday 04 November 2008 04:05:19  IST
#     REVISION:  ---
#===============================================================================

use strict;
use warnings;

my $ndistro = 1;

if (@ARGV >= 1)
{
    $ndistro = $ARGV[0];
    if ($ndistro > 100)
    {
        $ndistro = 100;
    }
}

my $lynx = `which lynx`;
chomp($lynx);
if ($lynx eq "")
{
    print STDERR "$0: please install lynx\n";
    print STDERR "sudo apt-get install lynx\n";
    exit(-1);
}

open(LYNX, "lynx -source http://distrowatch.com/ |") or die("$0: cannot open lynx: $!\n");

my $i = 1;

while ($i <= $ndistro)
{
    my $line;
    my $distro;
    my $rank = "";
    while ($line = <LYNX>)
    {
        chomp($line);
        $line =~ s/<th class=([^>]*)>(.*?)<\/th>/$2/i;
        $line =~ s/(\s+)//g;
        if ($line eq "$i")
        {
            $rank = $line;

            unless ($line = <LYNX>) {last;}
            chomp($line);
            $line =~ s/<td class=([^>]*)><a href=([^>]*)>(.*?)<\/a><\/td>/$3/i;
            $line =~ s/(\s+)//g;
            $distro = $line;

            print "$rank\t$distro\n";
            last;
        }
    }
    ++$i;
}

close(LYNX);

Sample runs of above program:
$ ./best_distro.pl
1       Ubuntu
$ ./best_distro.pl 5
1       Ubuntu
2       openSUSE
3       Mint
4       Fedora
5       Debian

Counts from min to max

In order to get counts from start number to end number,
I have written a shell script.

#!/bin/sh

if [ $# -ne 2 ]
then
echo "Usage: $0 min max"
exit
fi

min=$1
max=$2

while [ $min -le $max ]
do
echo -n $min " "
min=`expr $min + 1`
done
#end script

Sample run:
$ ~/bin/count.sh 2 5
2 3 4 5

Tip: This is very handy script, that is very helpful
in getting counts in the loop. For example:
$ for i in `~/bin/count.sh 2 8`
> do
> echo "Hello $i"
> done
Hello 2
Hello 3
Hello 4
Hello 5
Hello 6
Hello 7
Hello 8

Total RAM in your System

In order to find total RAM in your system, give following command:

$ cat /proc/meminfo | awk '/^MemTotal/ {print $2/1024 " MB"}'
2008.07 MB

If you all information related to memory:

$ cat /proc/meminfo


Extra: Total CPU cores in your system:

$ cat /proc/cpuinfo | awk '/^processor/ {ncores++} END {print "Total cores = " ncores}'
Total cores = 2

Finding Processes, which are Accessing a File System

After completing every task related to CD/DVD/USB, you might find it annoying to unmount/eject CD/DVD/USB, while it is being used by some unknown/stuck process. Therefore I am providing a solution (fuser). Suppose your were accessing CDROM mounted at /mnt/cd/.

To view which files (of CD) are being accessed by whom :
$ fuser -mu /mnt/cd/*

If you are sure that, the processes are stuck/hang. Then you can kill all those processes :
$ fuser -kmu /mnt/cd/*


Warning!!!: If you are using writable medium (like USB stick), please give following command before killing processes:
$ sudo sync

Retrieving Date and Time from Unix Timestamp

In Unix, we can retrieve Date and Time from Timestamp by using following command:

$ date -r 1220000000
Fri Aug 29 14:23:20 IST 2008

But in Linux, there is no '-r' option. Therefore, I have written a Perl script to
retrieve date and time from timestamp. Here is the script:

$ vi ~/bin/dater.pl

#!/usr/bin/perl -w

use strict;
use warnings;

my $ts = time;
if (@ARGV >= 1)
{
    $ts = $ARGV[0];
}
my ($sec, $min, $hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime($ts);
++$mon;
$year+=1900;
print "$mday-$mon-$year $hour:$min:$sec\n";


# end dater.pl

Sample runs of above program:
$ dater.pl
15-10-2008 12:34:37
$ dater.pl 1220000000
29-8-2008 14:23:20

PS: you can change parameters in print function in the program
according to output you desire.

Terminating Processes Containing Given Pattern

Generally, if you want to terminate a process which contains the given pattern, you use following 4 steps:

1. $ ps aux | grep pattern 
2. Copy the pid of the process from output of above command.
3. Paste this pid in the following command
4. $ kill -9 pid

The above procedure is cumbersome and requires much typing.

Therefore I have written a program to terminate process(es), which contains given pattern. (I am assuming that ~/bin is in your $PATH).

$ vi ~/bin/kill_prog.sh

#!/bin/sh

# Kills the program given

if [ $# -lt 2 ]
then
  echo "Usage: $0 [1/0] signal program-name"
  echo "[0/1] Do not Kill / Do kill (optional)"
  echo "signal -TERM (Graceful Terminate), -KILL (Abrupt KIll)"
  exit
fi

donothing=1
signal=$1
program=$2
if [ $# -gt 2 ]
then
  donothing=$1
  signal=$2
  program=$3
fi

pids=$(ps auxww | awk "/ $program / { print \$2 }")


for pid in $pids
do
  if [ $donothing -eq 1 ] ; then
  echo "kill $signal $pid"
  else
  kill $signal $pid
  fi
done

#end kill_prog.sh

By default, this program does not kills the process. You have to

pass 0 as second parameter to the command to kill.

Sample runs of above programs:

$ kill_prog.sh
Usage: /home/mitesh/Programming/Shell/WCS/kill_prog.sh [1/0] signal program-name
[0/1] Do not Kill / Do kill (optional)
signal -TERM (Graceful Terminate), -KILL (Abrupt KIll)
$ kill_prog.sh -TERM ping
kill -TERM 16050
$ kill_prog.sh -KILL ping
kill -KILL 16050
$ kill_prog.sh 1 -KILL ping
kill -KILL 16050
$ kill_prog.sh 0 -KILL ping
Killed

The last command actually terminates(-TERM) or kills(-TERM).

Shell Session Recording

In order to record the commands and their output in a shell session,
you can use script command. For example:

[mitesh@linuxbox:370:~]$ script
Script started, file is typescript
[mitesh@linuxbox:370:~]$ ls
CvsRoot Desktop Documents Download Examples linux Music PDF Pictures Programming Public Templates typescript Videos workspace
[mitesh@linuxbox:371:~]$ /bin/date
Fri Oct 3 16:51:42 IST 2008
[mitesh@linuxbox:372:~]$ whoami
mitesh
[mitesh@linuxbox:373:~]$ exit
exit

Script done, file is typescript

You can view the output file typescript file using your favorite editor.
$ cat typescript
Script started on Friday 03 October 2008 04:51:27 PM IST
[mitesh@linuxbox:370:~]$ ls
CvsRoot Desktop Documents Download Examples linux Music PDF Pictures Programming Public Templates typescript Videos workspace
[mitesh@linuxbox:371:~]$ /bin/date
Fri Oct 3 16:51:42 IST 2008
[mitesh@linuxbox:372:~]$ whoami
mitesh
[mitesh@linuxbox:373:~]$ exit
exit

Script done on Friday 03 October 2008 04:51:54 PM IST

PS: you can save the output to any file, you want instead of typescript in
current directory. For example
$ script shell_session_20081003.log
...
...
$ exit
$ cat shell_session_20081003.log