Linux Tips

Video Cutter V2: Video Cutting Using Mencoder

2012-02-13T00:03:00.001+05:30

I have upgraded the Video Cutter program. Now it has 2 more features:
1. Strict Mode (-s flag): In this mode, strict monotonously increasing order of times must be given in the configuration (default: video_cutter.conf) file.
2. Joining Split Videos (-j flag): When this flag is given with the command, it does join the split video files into a single video file.

Here is the updated version of the earlier perl script:


#!/usr/bin/perl -w
#===============================================================================
#
#         FILE:  video_cutter.pl
#
#        USAGE:  ./video_cutter.pl [options] <input_video_file>
#
#  DESCRIPTION:  
#
#      OPTIONS:  ---
# REQUIREMENTS:  ---
#         BUGS:  ---
#        NOTES:  ---
#       AUTHOR:  Mitesh Singh Jat (mitesh), <mitesh[at]yahoo-inc[dot]com>
#      VERSION:  2.0
#      CREATED:  02/12/2011 03:57:55 PM IST
#===============================================================================

use strict;
use warnings;

use Getopt::Std;

sub usage()
{
    print STDERR "USAGE: $0 [options] <input_video_file>\n";
    print STDERR "          -c <conf_file>    default  /base_dir/input_video_file/video_cutter.conf\n";
    print STDERR "                            Start_time(hh:mm:ss),End_time(hh:mm:ss)\n\n";
    print STDERR "          -o <out_dir>      default  /base_dir/input_video_file/\n";
    print STDERR "          -s                strict format check for conf files     [default: no checking]\n";
    print STDERR "          -j                Join output splits into one video file [default: no joining]\n";
}

sub hms_to_seconds()
{
    my $end_sec = 0;
    my ($h, $m, $s) = split(/:/, $_[0]);
    $s = defined($s) ? $s : 0;
    $end_sec += $s;
    $m = defined($m) ? $m : 0;
    $end_sec += (60 * $m);
    $h = defined($h) ? $h : 0;
    $end_sec += (60 * 60 * $h);
    return($end_sec);
}

sub check_times_in_file()
{
    my $conf_file = $_[0];
    open(FH, "$conf_file") or die("$0: Cannot open '$conf_file'\n");
    my $line;
    my $nline = 0;
    my $prev_end_sec = -1;
    while ($line = <FH>)
    {
        chomp($line);
        ++$nline;
        next if ($line =~ m/^#/);
        my ($start_time, $end_time) = split(/,/, $line);
        if (!defined($end_time))
        {
            print STDERR "$0: End time(HH:MM:SS) is not present in line no $nline: $line\n";
            close(CFH);
            return;
        }
        my ($h, $m, $s) = split(/:/, $start_time);
        if (!defined($s))
        {
            print STDERR "$0: Start time is not in format (HH:MM:SS) line no $nline: $line\n";
            close(CFH);
            return;
        }
        ($h, $m, $s) = split(/:/, $end_time);
        if (!defined($s))
        {
            print STDERR "$0: End time is not in format (HH:MM:SS) line no $nline: $line\n";
            close(CFH);
            return;
        }

        my $start_sec = &hms_to_seconds($start_time);
        my $end_sec = &hms_to_seconds($end_time);
        if ($start_sec >= $end_sec)
        {
            print STDERR "$0: $start_sec >= $end_sec in line no $nline: $line\n";
            close(CFH);
            return;
        }
        if ($prev_end_sec >= $start_sec)
        {
            print STDERR "$0: $prev_end_sec >= $start_sec in line no $nline: $line and prev line\n";
            close(CFH);
            return;
        }
        $prev_end_sec = $end_sec;
    }
    close(FH);
    return ($nline);
}

my %opts;
getopt('o:c:', \%opts);

foreach my $opt (sort keys %opts)
{
    if (!defined($opts{$opt}))
    {
        print STDERR "$0: Requires value for option '$opt'\n";
        &usage();
        exit(-1);
    }
}

if (@ARGV != 1)
{
    &usage();
    exit(-1);
}

my $input_video_file = "$ARGV[0]";
my $out_dir = `dirname $input_video_file`;
chomp($out_dir);
my $conf_file = "$out_dir/video_cutter.conf";
my $strict_checking = 0;
my $join_outputs = 0;
my $out_video_files = "";

if (defined($opts{"c"}))
{
    $conf_file = $opts{"c"};
}
if (defined($opts{"o"}))
{
    $out_dir = $opts{"o"};
}
if (defined($opts{"s"}))
{
    $strict_checking = 1;
}
if (defined($opts{"j"}))
{
    $join_outputs = 1;
}

unless (-f "$input_video_file")
{
    print STDERR "$0: Input video file '$input_video_file' is not present\n";
    exit(-1);
}
unless (-f "$conf_file")
{
    print STDERR "$0: split conf file '$conf_file' is not present\n";
    exit(-1);
}
unless (-d "$out_dir")
{
    print STDERR "$0: out dir '$out_dir' is not present\n";
    exit(-1);
}
unless (-w "$out_dir")
{
    print STDERR "$0: out dir '$out_dir' is not writable\n";
    exit(-1);
}

my $mencoder = "/usr/local/bin/mencoder";
unless (-x $mencoder)
{
    $mencoder = "/usr/bin/mencoder";
}
unless (-x $mencoder)
{
    print STDERR "$0: please install mencoder\n";
    print STDERR "sudo apt-get install mencoder\n";
    exit(-1);
}

open(CFH, "$conf_file") or die("$0: Cannot open '$conf_file'\n");
my $line;
my $nline = 0;
my $nsplit = 0;
my $split_name = `basename $input_video_file`;
chomp($split_name);
$split_name =~ s/\.[^.]*$//;
my $split_ext = $input_video_file;
$split_ext =~ s/.*\.([^.]*)$/$1/;
my $success = 0;

if ($strict_checking == 1)
{
    print "Strict Mode\n";
    my $retval = &check_times_in_file($conf_file);
    if (!defined($retval))
    {
        print STDERR "$0: Problem in conf file \"$conf_file\"\n";
        exit(-1);
    }
}
while ($line = <CFH>)
{
    chomp($line);
    $nline++;
    next if ($line =~ m/^#/);
    my ($start_time, $end_time) = split(/,/, $line);
    next if (!defined($end_time));
    my $start_sec = &hms_to_seconds($start_time);
    my $end_sec = &hms_to_seconds($end_time);
    if ($start_sec >= $end_sec)
    {
        print STDERR "$0: $start_sec >= $end_sec\n";
        print STDERR "    $start_time >= $end_time ... skipping for line no $nline ...\n";
        next;
    }
    $end_sec -= $start_sec;
    my $cmd = sprintf("%s -ss %d -endpos %d -ovc copy -oac copy -o %s/%s_%03d.%s %s", 
            $mencoder, $start_sec, $end_sec, $out_dir, $split_name, $nsplit,
            $split_ext, $input_video_file);
    print "\n\n";
    print "-" x 80 . "\n";;
    print "$cmd\n";
    system("$cmd");
    if ($? != 0)
    {
        print STDERR "$0: failed to create $nsplit split for line no $nline\n";
        print STDERR "\t$cmd\n";
    }
    else
    {
        print STDOUT "Created $nsplit split for line $nline\n";
        $out_video_files .= sprintf(" %s/%s_%03d.%s", $out_dir, $split_name, $nsplit, $split_ext);
        $success++;
    }
    print "-" x 80 . "\n";;
    $nsplit++;
}

close(CFH);

print "\n";
print "=" x 80 . "\n";;
printf("Total lines = %d,   Success = %d/%d,  Failure = %d/%d\n",
        $nline, $success, $nsplit,
        $nsplit - $success, $nsplit);
print "=" x 80 . "\n";;

if ($join_outputs == 1)
{
    if ($success < 1)
    {
        print STDERR "$0: failed to join video files.\n";
        exit(-1);
    }
    my $joined_video_file = sprintf("%s/%s_joined.%s", $out_dir, $split_name, $split_ext);
    my $cmd = sprintf("%s -ovc copy -oac copy -o %s %s", 
            $mencoder, $joined_video_file, $out_video_files);
    print "\n\n";
    print "-" x 80 . "\n";;
    print "Joining Video Files into $joined_video_file\n";
    print "-" x 80 . "\n";;
    print "$cmd\n";
    system("$cmd");
    if ($? != 0)
    {
        print STDERR "$0: failed to create joined video file $joined_video_file\n";
        print STDERR "\t$cmd\n";
    }
    else
    {
        print STDOUT "Created joined video file $joined_video_file\n";
    }
    print "-" x 80 . "\n";;
}

exit(0);

Video Cutter: Video Cutting using Mencoder

2011-06-27T00:07:00.004+05:30

I have written a perl script, then can split/cut parts from a video file.

#!/usr/bin/perl -w
#===============================================================================
#
#         FILE:  video_cutter.pl
#
#        USAGE:  ./video_cutter.pl [options] <input_video_file>
#
#  DESCRIPTION:  
#
#      OPTIONS:  ---
# REQUIREMENTS:  ---
#         BUGS:  ---
#        NOTES:  ---
#       AUTHOR:  Mitesh Singh Jat (mitesh), <mitesh[at]yahoo-inc[dot]com>
#      VERSION:  1.0
#      CREATED:  06/26/2011 03:57:55 PM IST
#     REVISION:  ---
#===============================================================================

use strict;
use warnings;

use Getopt::Std;

sub usage()
{
   print STDERR "USAGE: $0 [options] <input_video_file>\n";
   print STDERR "          -c <conf_file>    default  /base_dir/input_video_file/video_cutter.conf\n";
   print STDERR "                            Start_time(hh:mm:ss),End_time(hh:mm:ss)\n\n";
   print STDERR "          -o <out_dir>      default  /base_dir/input_video_file/\n";
}

sub hms_to_seconds()
{
   my $end_sec = 0;
   my ($h, $m, $s) = split(/:/, $_[0]);
   $s = defined($s) ? $s : 0;
   $end_sec += $s;
   $m = defined($m) ? $m : 0;
   $end_sec += (60 * $m);
   $h = defined($h) ? $h : 0;
   $end_sec += (3600 * $h);
   return($end_sec);
}

my %opts;
getopt('o:c:', \%opts);

foreach my $opt (sort keys %opts)
{
   if (!defined($opts{$opt}))
   {
       print STDERR "$0: Requires value for option '$opt'\n";
       &usage();
       exit(-1);
   }
}

if (@ARGV != 1)
{
   &usage();
   exit(-1);
}

my $input_video_file = "$ARGV[0]";
my $out_dir = `dirname $input_video_file`;
chomp($out_dir);
my $conf_file = "$out_dir/video_cutter.conf";

if (defined($opts{"c"}))
{
   $conf_file = $opts{"c"};
}
if (defined($opts{"o"}))
{
   $out_dir = $opts{"o"};
}

unless (-f "$input_video_file")
{
   print STDERR "$0: Input video file '$input_video_file' is not present\n";
   exit(-1);
}
unless (-f "$conf_file")
{
   print STDERR "$0: split conf file '$conf_file' is not present\n";
   exit(-1);
}
unless (-d "$out_dir")
{
   print STDERR "$0: out dir '$out_dir' is not present\n";
   exit(-1);
}
unless (-w "$out_dir")
{
   print STDERR "$0: out dir '$out_dir' is not writable\n";
   exit(-1);
}

my $mencoder = "/usr/local/bin/mencoder";
unless (-x $mencoder)
{
   $mencoder = "/usr/bin/mencoder";
}
unless (-x $mencoder)
{
   print STDERR "$0: please install mencoder\n";
   print STDERR "sudo apt-get install mencoder\n";
   exit(-1);
}

open(CFH, "$conf_file") or die("$0: Cannot open '$conf_file'\n");
my $line;
my $nline = 0;
my $nsplit = 0;
my $split_name = `basename $input_video_file`;
chomp($split_name);
$split_name =~ s/\.[^.]*$//;
my $split_ext = $input_video_file;
$split_ext =~ s/.*\.([^.]*)$/$1/;
my $success = 0;
while ($line = <CFH>)
{
   chomp($line);
   $nline++;
   next if ($line =~ m/^#/);
   my ($start_time, $end_time) = split(/,/, $line);
   next if (!defined($end_time));
   my $start_sec = &hms_to_seconds($start_time);
   my $end_sec = &hms_to_seconds($end_time);
   if ($start_sec >= $end_sec)
   {
       print STDERR "$0: $start_sec >= $end_sec\n";
       print STDERR "    $start_time >= $end_time ... skipping for line no $nline ...\n";
       next;
   }
   $end_sec -= $start_sec;
   my $cmd = sprintf("%s -ss %d -endpos %d -ovc copy -oac copy -o %s/%s_%03d.%s %s",
           $mencoder, $start_sec, $end_sec, $out_dir, $split_name, $nsplit,
           $split_ext, $input_video_file);
   print "\n\n";
   print "-" x 80 . "\n";;
   print "$cmd\n";
   system("$cmd");
   if ($? != 0)
   {
       print STDERR "$0: failed to create $nsplit split for line no $nline\n";
       print STDERR "\t$cmd\n";
   }
   else
   {
       print STDOUT "Created $nsplit split for line $nline\n";
       $success++;
   }
   print "-" x 80 . "\n";;
   $nsplit++;
}

close(CFH);

print "\n";
print "=" x 80 . "\n";;
printf("Total lines = %d,   Success = %d/%d,  Failure = %d/%d\n",
       $nline, $success, $nsplit,
       $nsplit - $success, $nsplit);
print "=" x 80 . "\n";;

exit(0);

Please place the above perl script (video_cutter.pl) in any directory present in $PATH.

Sample Run:

Usage of the above script.

$ video_cutter.pl 
USAGE: /home/mitesh/Programming/Perl/WCS/video_cutter.pl [options] 
         -c     default  /base_dir/input_video_file/video_cutter.conf
                           Start_time(hh:mm:ss),End_time(hh:mm:ss)

         -o       default  /base_dir/input_video_file/

Content of a sample config file, specifying the split timings.
This will create 3 splits, of 0s-90s, 140s-210s, and 240s-End.

$ cat test_video.conf 
00:00:00,00:01:30
00:02:20,00:03:30
00:04:00,59:59:00

Now, it will create the three split files in ~/Video/test/ directory.

$ video_cutter.pl -c test_video.conf -o ~/Video/test test_video.vob 


--------------------------------------------------------------------------------
/usr/local/bin/mencoder -ss 0 -endpos 90 -ovc copy -oac copy -o /home/mitesh/Video/test/test_video_000.vob test_video.vob
MEncoder 1.0rc4-4.4.5 (C) 2000-2010 MPlayer Team
...
...
...
Created 2 split for line 3
--------------------------------------------------------------------------------

================================================================================
Total lines = 3,   Success = 3/3,  Failure = 0/3
================================================================================
$ ls -l ~/Video/test/*.vob
-rw-r--r-- 1 mitesh mitesh   7519672 Jun 27 00:31 /home/mitesh/Video/test/test_video_000.vob
-rw-r--r-- 1 mitesh mitesh   5844598 Jun 27 00:31 /home/mitesh/Video/test/test_video_001.vob
-rw-r--r-- 1 mitesh mitesh 570855360 Jun 27 00:30 /home/mitesh/Video/test/test_video_002.vob

CPU Frequency Scaling

2011-05-24T14:11:00.006+05:30

I have written a small shell script to increase or decrease CPU frequency. By default, it shows current CPU Frequency Scaling Governor. This can be changed only by root user. So this script needs to be run as root user or sudo as root, while changing the CPU Frequency Scaling governor.

#!/bin/bash

available_governors=$(cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_available_governors \
            | head -1 | sed -e 's/ \([a-zA-Z0-9]\)/|\1/g' -e 's/ $//')
if [ $# -ne 1 ]
then
  
   echo "USAGE: $0 [$available_governors]"
fi

echo "Command line to change CPU Scaling."
echo "                    - By Mitesh Singh Jat"
echo ""

## CPU Governor path
#/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
function current_cpu_governor ()
{
   echo -n "Current CPU Scaling Governor is: "
   cpu_scaling_governor="NOT SET"
   for governor in $(ls /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor)
   do
       cpu_scaling_governor=$(cat $governor)
   done
   echo "$cpu_scaling_governor"
}

current_cpu_governor;

## Exit, if no governor is provided
new_governor=""
if [ $# -eq 0 ]
then
   exit 0
else
   new_governor="$1"
fi

## Run as root always
user_id=`whoami`
if [[ "$user_id" != "root" ]]
then
   echo "$0: please run this script as root user."
   exit
fi 

if [ -z $(echo $available_governors | sed -e 's/^/|/' -e 's/$/|/' | grep "|$new_governor|") ]
then
   echo "Sorry, this mode '$new_governor' is not supported."
   exit 1
else
   echo "Setting CPU into '$new_governor' Mode..."
fi
## Now set cpu governor to the given mode
for governor in $(ls /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor)
do
   echo "$new_governor" > $governor
done
current_cpu_governor;

exit 0

Sample Run

Getting current CPU Frequency Scaling Governor
$ cd /path/where/cpu_scaling.sh/is/copied/
$ ./cpu_scaling.sh
USAGE: ./cpu_scaling.sh [powersave|conservative|ondemand|userspace|performance]
Command line to change CPU Scaling.
                   - By Mitesh Singh Jat

Current CPU Scaling Governor is: ondemand


Increasing CPU frequency (Please run as root).
$ ./cpu_scaling.sh performance
Command line to change CPU Scaling.
                   - By Mitesh Singh Jat

Current CPU Scaling Governor is: ondemand
./cpu_scaling.sh: please run this script as root user.
$ sudo ./cpu_scaling.sh performance
[sudo] password for mitesh:
Command line to change CPU Scaling.
                   - By Mitesh Singh Jat

Current CPU Scaling Governor is: ondemand
Setting CPU into Performance Mode...
Current CPU Scaling Governor is: performance
$ ./cpu_scaling.sh
USAGE: ./cpu_scaling.sh [powersave|conservative|ondemand|userspace|performance]
Command line to change CPU Scaling.
                   - By Mitesh Singh Jat

Current CPU Scaling Governor is: performance


Decreasing CPU frequency
$ sudo ./cpu_scaling.sh ondemand
Command line to change CPU Scaling.
                   - By Mitesh Singh Jat

Current CPU Scaling Governor is: performance
Setting CPU into OnDemand Mode...
Current CPU Scaling Governor is: ondemand

Playing only Audio from a Video File

2011-03-11T14:02:00.001+05:30

If you want to play only audio from a video file (say xyz.avi),
please provide -vo null in mplayer, given as:


 $ mplayer -vo null xyz.avi

Speeding up Disk Performance

2011-03-09T13:56:00.002+05:30

We can increase Hard Disk performance by ~40%, and decrease power consumption by Hard Disk, if we provide "noatime,nodiratime" options during partition mounting. Actually what happens is: whenever a file/directory is accessed, its atime "access time" is updated with epoch. These two options prevent these not-so-useful disk accesses. Hence
performance improvement.

The sample mount point (/home) entry in /etc/fstab may look like:

$ cat /etc/fstab | grep home
/dev/sda2 /home ext3 defaults,noatime,nodiratime 0 0

Windows XP in Grub 2

2011-02-24T10:49:00.003+05:30

When I installed Debian 6.0 (Squeeze) on my laptop, I found that Debian Installer had not added Windows XP entry in the GRUB 2. You might also face same issue, then you can add following lines in /boot/grub/grub.cfg


## (1) Windows XP in /dev/sda1
menuentry "Windows XP" {
    set root=(hd0,1)
    chainloader +1
}

Here are few tips how to set root in the grub.cfg



# DEVICE NAME CONVERSIONS
#
#  Linux           Grub
# -------------------------
#  /dev/fd0        (fd0)
#  /dev/sda        (hd0)
#  /dev/sdb2       (hd1,2)
#  /dev/sda3       (hd0,3)
#

Cleaning of Temporary Install Files in Ubuntu/Debian

2010-02-02T20:56:00.001+05:30

Cleaning of Temporary Install Files in Ubuntu/Debian can be done by giving
following commands:

$ sudo apt-get autoclean; sudo apt-get autoremove

How to change boot order in GRUB2?

2009-12-15T16:50:00.001+05:30

With Ubuntu 9.10 (Karmic Koala), GRUB2 is the default boot loader.
How to change boot order in GRUB2?

1.
$ cat /etc/grub/grub.cfg
see the order of the wanted kernel. Starts from 0.

2.
$ vi /etc/default/grub
change GRUB_DEFAULT=0 value to wanted kernel

3. run
$ update-grub
to update

4. reboot and check with
$ uname -r
to see if correct kernel selected.

Find Biggest Files/Directories

2009-12-07T12:34:00.002+05:30

Since ls does not give correct size on disk, better to
use du command.


$ du /path/to/dir | sort -nr

I hope above
command will give you the proper result you wanted.

Note: The above command may take large time, depending on

number of files in /path/to/dir . You can use depth(say 2) in
that dir.


$ du --max-depth=2 /path/to/dir | sort -nr

Newer Yahoo! Messenger Protocol on Pidgin on Debian Lenny 5.0

2009-11-17T17:23:00.002+05:30

Yahoo! has changed authentication method of Yahoo! messenger protocol, which is not supported in Pidgin (Version <>= 2.5.7) supports newer Yahoo! Messenger Protocol. But Debian 5.0 Lenny repository has older pidgin (2.4.3). We can install newer pidgin, in the following steps:


## download latest pidgin from pidgin.im (at this time 2.6.3 is latest)
$ wget http://sourceforge.net/projects/pidgin/files/Pidgin/pidgin-2.6.3.tar.bz2

## extract files using tar
$ tar -zxvf pidgin-2.6.3.tar.bz2

$ cd pidgin-2.6.3

## Configure, Compile, and make
$ ./configure --disable-screensaver --disable-vv --disable-avahi --disable-tcl --disable-tk --prefix=/usr 
$ make
$ sudo make install

Now you can use newer pidgin with newer Yahoo! Messenger. :)
Enjoy Yahoo!

Find Files Created Between 2 Times

2009-11-17T11:40:00.002+05:30

In order to find files created between two times (start hour and end hour). The required hours are hours from current time. For example,

Current time = 2 PM = 14:00

If you want file created between 9 AM and 12 PM today, the start hour and end hour are:

Start Hour = (14 - 9) = 5
End Hour = (14 - 12) = 2

Hence required command is:


$  ./find_files_between_times.pl /path/to/dir 5 2

The Perl script which does this is given below:-



#!/usr/bin/perl -w
#===============================================================================
#
#         FILE:  find_files_between_times.pl
#
#        USAGE:  ./find_files_between_times.pl <dir> <start_hour> <end_hour>
#
#  DESCRIPTION:  
#
#      OPTIONS:  ---
# REQUIREMENTS:  ---
#         BUGS:  ---
#        NOTES:  ---
#       AUTHOR:  Mitesh Singh Jat (mitesh), <mitesh[at]yahoo-inc[dot]com>
#      COMPANY:  Yahoo Inc, India
#      VERSION:  1.0
#      CREATED:  11/13/2009 10:00:02 PM IST
#     REVISION:  ---
#===============================================================================

use strict;
use warnings;

if (@ARGV != 3)
{
    print STDERR "Usage: $0 <dir> <start_hour> <end_hour>\n";
    exit(-1);
}

my $dir = $ARGV[0];
## Calculate current_hour - given_hour
#my $start_time = `/bin/date "+\%H"`;
my $start_time = $ARGV[1];
#chomp($start_time);
my $end_time = $ARGV[2];
$end_time = time - ($end_time * 60 * 60);
#$end_time = $start_time - $end_time;
#$start_time = $start_time - $ARGV[0];

if ($start_time > $end_time)
{
    ($start_time, $end_time) = ($end_time, $start_time);
}

my $cmd = "find $dir -ctime -$start_time";
print "Running $cmd\n";
my @files = `$cmd`;
foreach my $file (@files) # (`find $dir -ctime $start_time`)
{
    chomp($file);
    my ($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size,
                           $atime,$mtime,$ctime,$blksize,$blocks) 
        = stat($file);

    if ($ctime > $end_time)
    {
        next;
    }
    print "$file\n";
}


exit(0);

Better Console Calculator Using bc

2009-10-26T19:29:00.004+05:30

If we use expr for mathematical calculations on console (terminal), it is frustrating, and hard to remember syntax and escape sequences used in expr. :( This small tip will help us.

Just add following line in your .bashrc file (~/.bashrc).


function calc
{
echo "${1}" | bc -l;
}

Then update the shell environment by:


$ source ~/.bashrc

"calc" from the shell will work as follows:


$ calc 2+3
5
$ calc 1+2*3
7
$ calc 1.1*2
2.2
$ calc "(1+2)*3"
9
$ calc "(1+2)^3"
27
$ calc "s(.5)"
.47942553860420300027

Checking Network Services Using Telnet

2009-10-23T09:28:00.002+05:30

Suppose we want to check whether the web server(port 80) or any other network service is running or not, but we do not have any browsers (lynx, Firefox, IE, Netscape, ...), then there is a simple way of doing that. Just telnet to that machine on the http port (port no. 80 in general).


$ telnet <ip_addr> <port_no>

And then, give command "get /" (without quotes). If the webserver is running, it displays the HTML script of the homepage or basic info and closes the connection to the remote host.



$ telnet wordpress.com 80 
Trying 76.74.254.126...
Connected to wordpress.com.
Escape character is '^]'.
get /
<html>
<head><title>400 Bad Request</title></head>
<body bgcolor="white">
<center><h1>400 Bad Request</h1></center>
<hr><center>nginx</center>
</body>
</html>
Connection closed by foreign host.

Joining Multiple Videos into One Using Mplayer

2009-10-20T12:33:00.002+05:30

In order to join multiple video files, into a single video file, you just need to issue following command:



$ mencoder -oac copy -ovc copy -o joined_single_video.avi video1.avi video2.avi video3.avi

Even you can use wild cards (*, ?) too.



$ mencoder -oac copy -ovc copy -o joined_single_video.avi video*.avi

PS. In place of 'avi', you can give whatever file format is available.

Converting Improper mp3 into Proper mp3 for Nokia E71

2009-10-05T14:41:00.002+05:30

The music player of Nokia E71 is vulnerable to improper mp3. It stucks forever, even if there is a single improper mp3. Improper mp3 is a mp3 file which does not conform to mp3 standard, there are some problem in mp3 headers. For more information on improper mp3, please read manual of checkmp3 command.

$ man checkmp3

I have written a shell script which converts improper mp3's into proper mp3.



#!/bin/bash

## Script to fix mp3 files using checkmp3

## Checking existance of checkmp3
checkmp3=`which checkmp3`

if [[ "$checkmp3" == "" ]]
then
    echo "$0: please install checkmp3."
    exit
fi

if [ $# -ne 1 ]
then
    echo "USAGE: $0 <mp3_file|dir_with_mp3s>"
    exit
fi

dir="$1"
file=""

if [[ -d "$dir" ]]
then
    echo "processing directory '$dir'"
    temp_file="$dir/fixed.mp3"
    for file in `find "$dir" -iname "*.mp3" | sed 's/ /\\\_/g'`
    do
        file=`echo "$file" | sed 's/\\\_/ /g'`
        echo "processing file '$file'"
        $checkmp3 -i -sf "$file" > "$temp_file"
        if [ $? -ne 0 ]
        then
            echo "$0: error in processing file '$file'"
        else 
            #eyeD3 "$temp_file"
            #$checkmp3 "$temp_file"
            mv "$temp_file" "$file"
        fi
    done
    rm -f "$temp_file"
else
    file="$dir"
    echo "processing file '$dir'"
    dir=`dirname "$file"`
    temp_file="$dir/fixed.mp3"
    echo "$temp_file"

    $checkmp3 -i -sf "$file" > "$temp_file"
    if [ $? -ne 0 ]
    then
        echo "$0: error in processing file '$file'"
    else 
        #eyeD3 "$temp_file"
        #$checkmp3 "$temp_file"
        mv "$temp_file" "$file"
    fi
fi
exit 0

Sample run:

$ ./fix_mp3.sh xyz.mp3
$ ./fix_mp3.sh /path/to/mp3/directory/

How to Change MAC Address

2009-09-30T12:23:00.005+05:30

Changing MAC address of a machine is called spoofing a MAC address or faking a MAC address. In linux, you can change MAC address of your machine. This is how it is done.

First find the physical MAC address of your machine by running the following command :

$ ifconfig -a | grep HWaddr
eth0  Link encap:Ethernet HWaddr 00:1f:f3:cc:c2:f9

The hexadecimal numbers in blue denote my machine's MAC address. Yours will be different.

Next, login as root in Linux and enter the following commands -


# ifconfig eth0 down
# ifconfig eth0 hw ether 00:11:22:33:44:55
# ifconfig eth0 up
# ifconfig eth0 | grep HWaddr

Note above that I have changed the MAC address to a different number highlighted in blue. 00:11:22:33:44:55 is the new MAC address I have provided for my Linux machine. You can choose any 48 bits hexadecimal address as your MAC address.

Disabling Macbook Pro Touchpad

2009-09-10T14:54:00.003+05:30

We may want to disable Macbook Pro (or any other Laptop) Touchpad, such cases are:
(i) We have connected a USB mouse, so we do not want to use touchpad for now.
(ii) While typing, there is no use of touchpad, if touchpad is too sensitive, the cursor keeps on jumping due to slight touch of palm or finger.

I have written a script to disable/enable touchpad (which is using synaptics driver).


#!/bin/bash

## Disable touchpad if USB Mouse is attached

SYNAPTICS=`which synclient`

if [[ "$SYNAPTICS" == "" ]]
then
    echo "$0: please install synaptics touchpad driver."
    echo "Also make sure that 'Option         \"SHMConfig\" \"on\"'"
    echo " is added in Touchpad device Section in /etc/X11/xorg.conf"
    exit
fi

USB_mouse_present=`grep -ic "usb.*mouse" /proc/bus/input/devices`
# if no USB Mouse; enable touchpad
if [ $USB_mouse_present -eq 0 ]
then
    $SYNAPTICS TouchpadOff=0
else
    $SYNAPTICS TouchpadOff=1
fi 

# if any parameter [on|off] is given, override previous command
if [ $# -ge 1 ]
then
    if [ "$1" = "on" ]
    then
        $SYNAPTICS TouchpadOff=0
    else
        $SYNAPTICS TouchpadOff=1
    fi
fi

exit 0

Sample Run:
Turn on touchpad


$ ./touchpad.sh on

Turn off touchpad


$ ./touchpad.sh off

If we have plugged USB mouse, then just give following command


$ ./touchpad.sh

On removing USB mouse, give following, the touchpad will be enabled automatically. :)


$ ./touchpad.sh

PS: The configuration for synaptics driver can be referred from here or here.

IP Masquerade and Network Address Translation (NAT)

2009-09-04T12:21:00.002+05:30

If we want to connect multiple computers to the Internet using single public IP Address, Masquerading (A form of NATing) helps us.

NAT describes the process of modifying the network addresses contained with datagram headers while they are in transit. IP masquerade is the name given to one type of network address translation that allows all of the hosts on a private network to use the Internet at the price of a single IP address.

IP masquerading allows you to use a private (reserved) IP network address on your LAN and have your Linux-based router perform some clever, real-time translation of IP addresses and ports. When it receives a datagram from a computer on the LAN, it takes note of the type of datagram it is, “TCP,” “UDP,” “ICMP,” etc., and modifies the datagram so that it looks like it was generated by the router machine itself (and remembers that it has done so). It then transmits the datagram onto the Internet with its single connected IP address. When the destination host receives this datagram, it believes the datagram has come from the routing host and sends any reply datagrams back to that address. When the Linux masquerade router receives a datagram from its Internet connection, it looks in its table of established masqueraded connections to see if this datagram actually belongs to a computer on the LAN, and if it does, it reverses the modification it did on the forward path and transmits the datagram to the LAN computer.

I have written a shell script, which converts a Linux box into a router. The script is written as:


#!/bin/bash

## Output interface: connected to Internet
out_iface=ppp0

## Run as root always
user_id=`whoami`

if [[ "$user_id" != "root" ]]
then
   echo "$0: please run this script as root user."
   exit
fi   

## Checking existance of iptables
IPTABLES=`which iptables`

if [[ "$IPTABLES" == "" ]]
then
   echo "$0: please install iptables."
   exit
fi   

if [ $# -ge 1 ]
then
   case "$1" in
       status)
           $IPTABLES -t nat -L
           exit 0
           ;;
       stop)
           ## Disabling Packet forwarding in kernel
           echo 0 > /proc/sys/net/ipv4/ip_forward
           echo "Flushing NAT MASQUERADE Entries"
           $IPTABLES -t nat -F
           exit 0
           ;;
       restart)
           $0 stop
           if [ $# -ge 2 ]
           then
               $0 start $2
           else   
               $0 start
           fi   
           ;;
       start)
           if [ $# -ge 2 ]
           then
               out_iface=$2
           fi   
           ## Enabling Packet forwarding in kernel
           echo 1 > /proc/sys/net/ipv4/ip_forward

           ## Enabling NAT Masquerade, if not enabled
           if [ -z "`$IPTABLES -t nat -L | grep MASQUERADE`" ]
           then
              
               $IPTABLES -t nat -A POSTROUTING -o $out_iface -j MASQUERADE
           fi   
           ;;
       *)
           echo "USAGE: $0 <start|status|restart|stop> [internet_interface]"
           exit 1
           ;;
esac           
else   
   echo "USAGE: $0 <start|status|restart|stop> [internet_interface]"
   exit 1
fi   

exit 0

Sample Runs:


$ ./NAT_Masquerade.sh
./NAT_Masquerade.sh: please run this script as root user.
$ sudo ./NAT_Masquerade.sh
USAGE: ./NAT_Masquerade.sh  [internet_interface]
$
Here, internet_interface is the interface which is connected to internet.
By default, ppp0 (Dial up) interface is taken.

$ sudo ./NAT_Masquerade.sh status
Chain PREROUTING (policy ACCEPT)
target     prot opt source               destination

Chain POSTROUTING (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination
$
Since Masquerade is not yet applied, Chain POSTROUTING rule is empty.

Applying IP Masquerade to internet_interface eth0.
$ sudo ./NAT_Masquerade.sh start eth0
$ sudo ./NAT_Masquerade.sh status
Chain PREROUTING (policy ACCEPT)
target     prot opt source               destination

Chain POSTROUTING (policy ACCEPT)
target     prot opt source               destination
MASQUERADE  all  --  anywhere             anywhere

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination
$ sudo ./NAT_Masquerade.sh stop
Flushing NAT MASQUERADE Entries
$

Fixing Wired Network (eth0) Ethernet

2009-08-31T11:33:00.003+05:30

While using Debian based systems(like Ubuntu), I often found that network manager just got into the way whenever I wanted to fix an internet connection. So, first thing to do is to kill the associated processes (kill -9) after you find the process ID by using ps. Or you can totally get rid of these packages (usually network-manager, network-manager-gnome in GNOME or knetworkmanager in KDE).

Then, edit /etc/network/interfaces file.


$ sudo vi /etc/network/interface

auto eth0

iface eth0 inet dhcp

again assuming that we want to have a DHCP based connection.

Then restart the network connection by issuing the following command:


$ sudo /etc/init.d/networking restart

Determining Bits of CPU and OS (32/64-bits)

2009-08-14T10:32:00.004+05:30

In order to determine whether OS/CPU is 32-bit or 64-bit,
you can use this shell script.


#!/bin/bash
echo -n "Running "

RES=`uname -a | grep 64`
if [ $? -eq 0 ]; then

    echo -n "64-bit "
else
    echo -n "32-bit "
fi
echo -n "operating system on a "

RES=`cat /proc/cpuinfo | grep " lm "`
if [ $? -eq 0 ]; then

    echo -n "64-bit "
else
    echo -n "32-bit "
fi
echo "machine"

Sample Run:

$ ./os_cpu.sh
Running 64-bit operating system on a 64-bit machine

Let Linux Speak Time and Day for You

2009-08-05T10:07:00.003+05:30

I have written a single line command that tells time of the day:

$ espeak "Time is `/bin/date \"+%H hours %M minutes %S seconds\"`"You need not to type this command every time, just run the

following commands only one time:$ echo "alias speak_time='espeak \"Time is \`/bin/date \"+%H hours %M minutes %S seconds\"\`\"'" >> ~/.bashrc $ source ~/.bashrc

Now, you will be able to run speak_time any number of time at any time, and you will get exact time. :-)

$ speak_time

PS: Requirement of above command is "espeak"

$ sudo apt-get install espeak

For speaking day, just add following alias in your .bashrc file

alias speak_day='espeak "Today is `/bin/date \"+%A, %d %B 20%y\"`"'

Mount Windows Shared Folder onto Linux Directory

2009-07-27T14:56:00.004+05:30

Suppose you want to mount Windows shared folder (say shared_folder) on windows machine (IP address 10.226.194.169) on a folder (say /local/smbshare/shared_folder), you just need to give following
command:

$ sudo mount -t smbfs -o username=domainname\\yourname,password=yoursecretpassword -o gid=users,dmask=777,fmask=777,rw //10.226.194.169/shared_folder /local/smbshare/shared_folder

You can verify whether the above command is successful or not, by using:
$ mount | grep shared_folder

If the above command shows some output, it means mount is successful :)

Mounted Filesystem Information

2009-07-12T12:00:00.003+05:30

For getting information of a partition (filesystem) which is mounted on a directory on Linux System, I have created a C program. Its listing is given as below:


/*
 * =====================================================================================
 *
 *       Filename:  file_system_stat.c
 *
 *    Description:  Get file system statistics of mounted partition
 *
 *        Version:  1.0
 *        Created:  Thursday 09 July 2009 10:48:02  IST IST
 *       Revision:  none
 *       Compiler:  gcc
 *
 *         Author:  Mitesh Singh Jat (mitesh)
 *
 * =====================================================================================
 */

#include <stdio.h>
#include <sys/statfs.h>

int file_system_stats(const char *pathp)
{
    struct statfs sfs;
    int retval;
    if (pathp == NULL)
    {
        fprintf(stderr, "file_system_stats: cannot find stats of NULL path\n");
        return (-1);
    }
    retval = statfs(pathp, &sfs);
    if (retval < 0)
    {
        fprintf(stderr, "file_system_stats: cannot find file system\n");
        fprintf(stderr, "    stats of partition %s\n", pathp);
        return (-1);
    }
    printf("\n=== Filesystem Stats of '%s' ===\n", pathp);
    printf("Optimal Transfer Block Size = %ld\n", sfs.f_bsize);
    printf("Total data blocks           = %ld\n", sfs.f_blocks);
    printf("Total free data blocks      = %ld\n", sfs.f_bfree);
    printf("Total file nodes            = %ld\n", sfs.f_files);
    printf("Total free file nodes       = %ld\n", sfs.f_ffree);
    printf("=================================================\n\n");
    return (retval);
}

int main(int argc, char *argv[])
{
    int i;
    int retval = 0;
    if (argc <= 1)
    {
        fprintf(stderr, "Usage: %s <path> [more_paths...]\n", argv[0]);
        retval = file_system_stats("./");
        return (retval);
    }

    for (i = 1; i < argc && retval >= 0; ++i)
    {
        retval = file_system_stats(argv[i]);
    }
    return (retval);
}

Compilation:
$ gcc -Wall -o file_system_stat file_system_stat.c

Sample Runs:
--(mitesh@roundduck-lm)-(~/Programming/C/Usp)--
--(0 : 505)$ ./file_system_stat
Usage: ./file_system_stat <path> [more_paths...]

=== Filesystem Stats of './' ===
Optimal Transfer Block Size = 4096
Total data blocks = 9690330
Total free data blocks = 3956097
Total file nodes = 2449408
Total free file nodes = 2315870
=================================================

--(mitesh@roundduck-lm)-(~/Programming/C/Usp)--
--(0 : 506)$ ./file_system_stat /boot

=== Filesystem Stats of '/boot' ===
Optimal Transfer Block Size = 4096
Total data blocks = 12017122
Total free data blocks = 5616343
Total file nodes = 3055616
Total free file nodes = 2830533
=================================================

--(mitesh@roundduck-lm)-(~/Programming/C/Usp)--
--(0 : 507)$ ./file_system_stat /boot /mnt/extra

=== Filesystem Stats of '/boot' ===
Optimal Transfer Block Size = 4096
Total data blocks = 12017122
Total free data blocks = 5616343
Total file nodes = 3055616
Total free file nodes = 2830533
=================================================

=== Filesystem Stats of '/mnt/extra' ===
Optimal Transfer Block Size = 4096
Total data blocks = 21235766
Total free data blocks = 7269970
Total file nodes = 5357568
Total free file nodes = 5357279
=================================================

--(mitesh@roundduck-lm)-(~/Programming/C/Usp)--
--(1 : 508)$ ./file_system_stat /this_is_not_a_partition
file_system_stats: cannot find file system
stats of partition /this_is_not_a_partition

Note: By the way, the block size of a filesystem can be found using commands given at here or here.

Removing Files With Unusual Characters

2009-07-01T19:23:00.002+05:30

Suppose, some one (miscreant) got access to your computer and
creates files, which you may not be able to delete or you will end
up deleting all the files/subdirectories of the directory on which
these files are created.

Some examples of such dangerous file names are:
$ ls -l
total 0K
-rw-r--r-- 1 mitesh users 0 2009-07-01 19:19 *
-rw-r--r-- 1 mitesh users 0 2009-07-01 19:20 -rf *
-rw-r--r-- 1 mitesh users 0 2009-07-01 19:27 -rw-r--r--
-rw-r--r-- 1 mitesh users 0 2009-07-01 19:19 test

Now, how are you going to delete above files?

(1) * : If one tries
$ rm *
or
$ rm -r *
This will delete all the files(& all subdirectories) in present working
directory.
Solution:
$ rm -f ./'*'
We can verify this.
$ ls -l
total 0K
-rw-r--r-- 1 mitesh users 0 2009-07-01 19:20 -rf *
-rw-r--r-- 1 mitesh users 0 2009-07-01 19:27 -rw-r--r--
-rw-r--r-- 1 mitesh users 0 2009-07-01 19:19 test

(2) -rf *: If one tries
$ rm -rf *
This will delete all the files & all subdirectories in present working
directory.
Solution:
$ rm -f ./'*'
We can verify this.
$ ls -l
total 0K
-rw-r--r-- 1 mitesh users 0 2009-07-01 19:27 -rw-r--r--
-rw-r--r-- 1 mitesh users 0 2009-07-01 19:19 test

(3) -rw-r--r--: If one tries
$ rm -rw-r--r--
rm: invalid option -- w
Try `rm ./-rw-r--r--' to remove the file `-rw-r--r--'.
Try `rm --help' for more information.
Solution:
$ rm ./-rw-r--r--
Other Solution
$ rm -- -rw-r--r--

Note: So we need to be vigilant, while using 'rm' command.

Finding Block Size of Filesystem

2009-06-26T15:22:00.003+05:30

In order to, find block size of a filesystem on Linux,

$ sudo tune2fs -l /dev/sda1 | grep -i 'block size'
Block size: 4096

OR

$ echo "mitesh"> test && du test | awk '{print $1}' && rm -f test
4K

Editing Very Very Large File

2009-06-25T15:54:00.003+05:30

Suppose we want to do changes in few lines in a very very large file. It is not possible to open such a big file(say size in GBs > RAM+Swap size) in a editor. Even sed/awk takes very long time, because they do pattern matching if mentioned on every line, otherwise, we can do one line editing with a line number. I have written a Perl Script to edit multiple lines independently. It uses sed commands to edit a line.

Format of Config file is:
line_number:sed_command


#!/usr/bin/perl -w
#===============================================================================
#
#         FILE:  ed_large_file.pl
#
#        USAGE:  ./ed_large_file.pl <config_file> <file_name> [overwrite}
#
#  DESCRIPTION:  Edit very[ very] large file
#
#      OPTIONS:  ---
# REQUIREMENTS:  ---
#         BUGS:  ---
#        NOTES:  ---
#       AUTHOR:  Mitesh Singh Jat (mitesh), <mitesh[at]yahoo-inc[dot]com>
#      VERSION:  1.0
#      CREATED:  Thursday 25 June 2009 02:32:37  IST IST
#     REVISION:  ---
#===============================================================================

use strict;
use warnings;

if (@ARGV < 2)
{
    print STDERR "$0: <config_file> <file_name> [overwrite]\n";
    print STDERR "!!!Be careful while using [overwrite] option,\n";
    print STDERR "because original file will be deleted.\n";
    exit(-1);
}

my $conf_file = $ARGV[0];
my $large_file = $ARGV[1];
my $overwrite = 0;
if (@ARGV >= 3 && $ARGV[2] eq "overwrite")
{
    $overwrite = 1;
}

my $temp_file = `dirname $large_file`;
chomp($temp_file);
if ($temp_file eq "" || (!(-d $temp_file)))
{
    print STDERR "$0: Cannot find dirname for temporary file.\n";
    print STDERR "Please check path of file '$large_file'\n";
    exit(-1);
}

$temp_file = $temp_file . "/temp";
print "Temporary file is '$temp_file'\n";

## Read config file
print "Reading config file '$conf_file'\n";
open(CFH, "$conf_file") or die("Cannot read Config file '$conf_file'\n");
my $line;
my %lineno_sedcmd;
while ($line = <CFH>)
{
    chomp($line);
    my ($lineno, $sedcmd) = split /:/, $line, 2;
    if (defined($sedcmd))
    {
        $lineno_sedcmd{$lineno} = $sedcmd;
        print "$lineno  $lineno_sedcmd{$lineno}\n";
        # Verifying sedcmd before running it;
        # it gives a chance to reedit config file
        my $cmd = "echo \"Mitesh Singh Jat\" | sed '$sedcmd' 1> /dev/null 2>&1";
        if (!(system($cmd) == 0))
        {
            print STDERR "$0: sed command '$sedcmd' for line '$lineno'";
            print STDERR "is having error. Please recheck with \$ man sed\n";
            close(CFH);
            exit(-1);
        }
    }
}
close(CFH);

my @line_nos;
foreach (sort keys (%lineno_sedcmd))
{
    push(@line_nos, $_);
}

## Open large file
open(LFH, "$large_file") or die("$0: Cannot open file '$large_file'");
## Temporary File 
open(OFH, ">$temp_file") or die("$0: Cannot create temporary file '$temp_file'");
my $nline = 0;
my $i = 0;
my $end_idx = @line_nos - 1;
print "Processing...";
while ($line = <LFH>)
{
    ++$nline;
    if ($line_nos[$i] == $nline)       # now edit
    {
        ++$i;   # This config line is over
        if ($i > $end_idx)
        {
            $i = $end_idx;
        }
        chomp($line);
        my $cmd = "echo \"$line\" | sed '$lineno_sedcmd{$nline}'";
        #print "$cmd\n";
        my $out_line = `$cmd`;
        print OFH "$out_line";
        print " $nline"; #sleep 1; # to see progress :)
    }
    else
    {
        print OFH "$line";
    }
}

print "\n";

close(OFH);
close(LFH);

if ($overwrite == 0)
{
    print "done\n";
    exit(0);
}

## Overwite original file by deleting it and moving temp
print "Overwriting...\n";
my $cmd = "rm -f $large_file \&\& mv $temp_file $large_file";
print "$cmd\n";
system($cmd) == 0 
    or die("Problem in overwriting. '$cmd' failed: $?\n");
print "done\n";    
exit(0);

Sample Run:



--(0 : 618)> ./ed_large_file.pl
./ed_large_file.pl: <config_file> <file_name> [overwrite]
!!!Be careful while using [overwrite] option,
because original file will be deleted.
--(mitesh@roundduck-lm)-(~/Programming/Perl/Editing_Large_Files)--
--(255 : 619)> cat large_file.txt
Shree Ganeshay Namah
Shri Bharat Singh Jat
Smt Amita Jat
Mitesh Jat
Shikha Jat
Shilpa Jat
This is garbage line. Please delete it.
--(mitesh@roundduck-lm)-(~/Programming/Perl/Editing_Large_Files)--
--(0 : 620)> cat large_file.conf
1:s/^.*$/!!&!!/
4:s/ / Singh /
7:/.*/d
--(mitesh@roundduck-lm)-(~/Programming/Perl/Editing_Large_Files)--
--(0 : 621)> ./ed_large_file.pl large_file.conf large_file.txt
Temporary file is './temp'
Reading config file 'large_file.conf'
1  s/^.*$/!!&!!/
4  s/ / Singh /
7  /.*/d
Processing... 1 4 7
done
--(mitesh@roundduck-lm)-(~/Programming/Perl/Editing_Large_Files)--
--(0 : 622)> cat ./temp
!!Shree Ganeshay Namah!!
Shri Bharat Singh Jat
Smt Amita Jat
Mitesh Singh Jat
Shikha Jat
Shilpa Jat
--(mitesh@roundduck-lm)-(~/Programming/Perl/Editing_Large_Files)--
--(0 : 623)> ./ed_large_file.pl large_file.conf large_file.txt overwrite
Temporary file is './temp'
Reading config file 'large_file.conf'
1  s/^.*$/!!&!!/
4  s/ / Singh /
7  /.*/d
Processing... 1 4 7
Overwriting...
rm -f large_file.txt && mv ./temp large_file.txt
done
--(mitesh@roundduck-lm)-(~/Programming/Perl/Editing_Large_Files)--
--(0 : 624)> cat large_file.txt
!!Shree Ganeshay Namah!!
Shri Bharat Singh Jat
Smt Amita Jat
Mitesh Singh Jat
Shikha Jat
Shilpa Jat
--(mitesh@roundduck-lm)-(~/Programming/Perl/Editing_Large_Files)--
--(0 : 625)>

Web Access through Proxy Server by Terminal Applications

2009-06-02T16:21:00.002+05:30

In many companies/Universities, the web access is granted through Proxy Server (Usually SQUID; hence port 3128).
There are many terminal applications (run on command line interface), which access Internet/Web. For example:
wget (to download file), ftp, lynx/links (to access website), apt/yum (to download and install package). If we are behind
proxy, these applications do not work. The easy solution is to set some shell environment variables, explained below:

For accessing web(lynx/links) using a non-authenticated proxy:
$ export http_proxy="http://proxy.yourcompany.com:3128"

Verify that the setting took place
$ echo $http_proxy
http://proxy.yourcompany.com:3128

For accessing web(lynx/links) using a authenticated proxy:
$ export http_proxy="http://username:password@proxy.yourcompany.com:3128"

If you want the change to be permanent (there each time you open a terminal),
add the export line to .bashrc in your 'home' directory.
$ echo 'export http_proxy="http://proxy.yourcompany.com:3128"'″ >> ~/.bashrc

Secure HTTP (over SSL) access
$ export https_proxy="https://proxy.yourcompany.com:3128"

FTP access
$ export ftp_proxy="ftp://proxy.yourcompany.com:3128"

Making Soundcard Work in Macbook Pro

2009-05-31T18:26:00.003+05:30

After installing Debian 5.0 (Lenny) on Macbook Pro (4,1), I found that
sound card was detected, but there was no sound. Then, I come to know
that, model=mbp3 option must be passed to snd-hda-intel kernel driver, to
make soundcard work. This is content of /etc/modprobe.d/sound file.


$ cat /etc/modprobe.d/sound

options snd slots=snd-hda-intel
# u1Nb.bVcdGDjFCiF:82801H (ICH8 Family) HD Audio Controller
alias snd-card-0 snd-hda-intel
# Add the following line as an option to snd_hda_intel module
options snd_hda_intel model=mbp3

Securing Your Root Using GRUB

2009-05-26T08:51:00.002+05:30

Generally, we forget to provide password security for GRUB boot loader.

If we do not provide password, any one can get access to root login without giving

root password, just by editing “kernel” parameters to “single” or “1″.

Therefore, you can prevent this editing by providing password.
$ grub-md5-crypt Password: Retype password: $1$BRvj2/$A0Xj.CeywUG/iL6j/15HC.
(you can provide any password, you want. But please remember this by heart)
and paste this output in /boot/grub/menu.lst below timeout
or default as

$vi /boot/grub/menu.lst ... timeout 10 ... password --md5 $1$BRvj2/$A0Xj.CeywUG/iL6j/15HC ...

Now, reboot and try to modify the kernel parameters. You will not be
able to until you press p and provide the password.

Macbook Pro Touchpad: Synaptics Configuration in xorg.conf

2009-05-22T09:09:00.003+05:30

I was trying to use touchpad on Macbook Pro (4,1) in Debian 5.0 (Lenny).
By default, it does not have tapping support, and multitouch support.
Even touchpad driver was also unavailable. Therefore, I had compiled
Linux kernel 2.6.29.3 added support for Apple Macbook Touchpad Driver.
Then after booting in new kernel with NVIDIA 8600 GT driver, I have
modified the xorg.conf with following lines.

## In case, you want to revert
$ sudo cp /etc/X11/xorg.conf /etc/X11/xorg.conf.bk
$ sudo vi /etc/X11/xorg.conf



...
Section "ServerLayout"
 Identifier     "Layout0"
 ...
 # Add Synaptics Touchpad as mouse
 InputDevice    "Synaptics Touchpad" "SendCoreEvents" #"CorePointer"
 InputDevice    "Mouse0" "CorePointer"
EndSection

...

Section "Module"
 ...
 # Load synaptics driver for Macbook Pro Touchpad
 Load           "synaptics"
EndSection

...

Section "InputDevice"
 Identifier      "Synaptics Touchpad"
 Driver          "synaptics"
 Option          "SendCoreEvents"        "true"
 Option          "Device"                "/dev/mouse0"
 Option          "Protocol"              "auto-dev"
 # not using edge scrolling
 Option          "HorizEdgeScroll"       "0"
 Option          "VertEdgeScroll"        "0"

 # use two finger scrolling
 Option          "VertTwoFingerScroll"   "1"
 Option          "HorizTwoFingerScroll"  "1" # set to 0 if you don't want horizontal scrolling

 # scroll speed, lower is faster
 Option          "HorizScrollDelta"      "15"
 Option          "VertScrollDelta"       "15"

 # minimum pressure motion factor
 Option          "PressureMotionMinZ"    "10"

 # touch and untouch thresholds, higher numbers if you like to push hard
 Option          "FingerLow"             "20"
 Option          "FingerHigh"            "60" # change to 30 or 40 if you like

 # FingerPress (Integer) : Above which counts as press
 Option          "FingerPress"           "130"

 # borders based on output from synclient
 Option          "LeftEdge"              "70"
 Option          "RightEdge"             "1120"
 Option          "TopEdge"               "50"
 Option          "BottomEdge"            "750"

 # speeds, smaller number for a slower mouse
 Option          "MinSpeed"              "0.8" # 0.5 is very slow, 1.5 is very fast
 Option          "MaxSpeed"              "1.3" # up to 1.5 works ok
 Option          "AccelFactor"           "0.10"

 # tap times, change to suit your tapping habits
 Option          "MaxTapMove"            "100"
 Option          "MaxTapTime"            "100"
 Option          "MaxDoubleTapTime"      "200"

 # don't change these or two finger tap stops working
 Option          "TapButton2"            "3"
 Option          "TapButton3"            "2"

 # must be commented out or normal tapping wont work
 #Option         "TapButton1"            "0"

 # Right Top Corner Button as right click
 Option          "RTCornerButton"        "2"
 Option          "RBCornerButton"        "0"

 # Left Top Corner Button as middle click
 Option          "LTCornerButton"        "3"
 Option          "LBCornerButton"        "0"

 # Palm Detection: Useful while typing
 Option          "PalmDetect"            "on"
 Option          "PalmMinWidth"          "10"
 Option          "PalmMinZ"              "200"

 # needed for disabled while typing fix
 Option          "SHMConfig"             "on"
EndSection
...

Pidgin: Buddy List Window Resize is not Working

2009-05-10T13:40:00.002+05:30

I am regular user of Pidgin Multiprotocol Instant Messenger (IM)
for Yahoo! and Gtalk IMs.
The buddy list window was getting wider and wider after several
uses. I tried to resize the window. But I was not able to do so.
Then I think to change the configuration file to resize the window.
The configurations are stored in ~/.purple/prefs.xml

I then, opened this file and searched for 'width'
The width in which I was interested is related to 'buddy list window'
i.e. look for section 'blist' and change the width variable according
to your need (I had set it to 300).
<pref name='blist'>
...
...
<pref name='width' type='int' value='300'/>
...
...
</pref>

Save this file and restart pidgin and viola!!
This Works :)

Sending stderr (Standard Error) to Pipe

2009-04-08T12:54:00.002+05:30

Many times we want to send output of standard error (stderr)
to pipe '|', so that we can use it as input for another command.

For example, while compilation of program, we are mostly interested
in error/warning messages. We can not get those lines by following
command:

$ make | egrep -i "error|warning"

so how can we can get only those error/warning message lines. We
just need to bind stderr (file handle 2) with stdout (file handle 1).
"2>&1"
The following example shows this:

$ make 2>&1 | egrep -i "error|warning"

Backup Using rsync

2009-03-29T10:43:00.006+05:30

There are many backup tools, but most are not as configurable as
rsync command. But still we may want more easiness to use rsync.
Therefore, I have written a Perl Script to use rsync for backing up
as many directories as you want. Here is a Perl script:


#!/usr/bin/perl 
#===============================================================================
#
#         FILE:  rsync_backup.pl
#
#        USAGE:  ./rsync_backup.pl [output_dir]
#
#  DESCRIPTION:  
#
#      OPTIONS:  ---
# REQUIREMENTS:  ---
#         BUGS:  ---
#        NOTES:  ---
#       AUTHOR:  Mitesh Singh Jat (mitesh), <mitesh[at]yahoo-inc[dot]com>
#      VERSION:  1.0
#      CREATED:  Saturday 28 March 2009 07:36:54  IST IST
#     REVISION:  ---
#===============================================================================

use strict;
use warnings;

my $rsync_include = "rsync_include.conf";
my $rsync_exclude = "rsync_exclude.conf";
my $out_dir = "/media/FreeAgent Drive";
if (@ARGV >= 1)
{
$out_dir = $ARGV[0];
}

unless (-f $rsync_include)
{
print STDERR "$0: Include config file $rsync_include is not present.";
exit(-1);
}
my $exclude_option = "--exclude-from=$rsync_exclude";
unless (-f $rsync_exclude)
{
print STDERR "$0: exclude config file $rsync_exclude is not present.";
$exclude_option = "";
}
unless (-d $out_dir)
{
print STDERR "$0: $out_dir Destination dir does not exists.\n";
exit(-1);
}
$out_dir =~ s/ /\\ /g;

open(FH, "$rsync_include") or die("$0: Cannot open $rsync_include\n");
my $line;
my $nlines = 0;
while ($line = <FH>)
{
my $command;
my $options = "";
chomp($line);
++$nlines;
if ($line =~ /^#/) # skip comments
{
    next;
}
my @fields = split(//, $line); # this junk char is Ctrl-X
if (@fields < 3)
{
    print "Not enough arguments in line $nlines\n";
    next;
}
if ($fields[2] =~ /^[Yy]/)  # sync
{
    $options .= " --delete --delete-excluded";
}
if (defined($fields[3]))
{
    $options .= " $fields[3]";
}

$fields[0] =~ s/<home>/\/home\/mitesh/;
$fields[1] =~ s/<home>/\/home\/mitesh/;
$fields[0] =~ s/<out_dir>/$out_dir/g;
$fields[1] =~ s/<out_dir>/$out_dir/g;

$command = "rsync -av $fields[0] $fields[1] $options ";
system($command) == 0  or die("$0: Error in running\n$command\n$!\n");
}
close(FH);
exit(0);

There are 2 configuration files, I have used for this script. Namely
1. rsync_include.conf
2. rsync_exclude.conf

Please place these 2 files in the directory, from where you are going
to run this script, else you can change path of these configuration
files in rsync_backup.pl .

Sample rsync_include.conf contains:
# Configuration file for backing up
#
# ^X is delimiter, which can be typed as Ctrl-V Ctrl-X
#src_folder^Xdest_folder^Xdelete_at_dest[Y/n]^Xother_rsync_options
#
## delete_at_dest =>
# y = sync // Use cautiously
# n = copy blindly
#
# Some tags that can be used:
## <home> = Home directory; change to your home directory in the script.
## <out_dir> = Common Destination Directory
#
/home/mitesh/Music^X<out_dir>^Xy^X
<home>/Documents^X<out_dir>^Xn^X
<home>/Programming^X<out_dir>^Xn^X
/home/mitesh/Videos^X<out_dir>^Xn^X
#/workspace/temp/*^X<out_dir>/temp^Xn^X
/mnt/extra/Extra/Films/*^X<out_dir>/Videos^Xn^X
/mnt/extra/Extra/Download/*^X<out_dir>/Videos^Xn^X

Sample rsync_exclude.conf contains:
.trash
Trash
Cache
.thumbnails
*.torrent

Sample run (I have placed above config files in ~/bin/):
$ cd ~/bin
$ ./rsync_backup.pl
...
or, if you want to use some backup directory on harddisk,
mounted on /media/disk (say, /media/disk/backup)
$ ./rsync_backup /media/disk/backup

Customizing Your Login Message With /etc/issue

2009-03-26T12:43:00.003+05:30

If you are bored with same login message at Linux console,
you can change it by changing /etc/issue file.

# clear > /etc/issue
# echo "This is Mitesh's Machine." >> /etc/issue

Even you can provide other details of your system, by using
single alphabet given here.

# echo "\d \m \s \v" >> /etc/issue

Fortune Status for Pidgin IM

2009-03-26T11:33:00.004+05:30

If you want to change status message of Pidgin Message by
fortune message. Just create a file pidgin_status_message.py
And copy the following lines.

#----------------------------

#!/usr/bin/env python
import dbus,subprocess,time

def set_status(message):
  bus = dbus.SessionBus()
  obj = bus.get_object("im.pidgin.purple.PurpleService", "/im/pidgin/purple/PurpleObject")
  purple = dbus.Interface(obj, "im.pidgin.purple.PurpleInterface")
  current = purple.PurpleSavedstatusGetType(purple.PurpleSavedstatusGetCurrent())
  status = purple.PurpleSavedstatusNew("", current)
  purple.PurpleSavedstatusSetMessage(status, message)
  purple.PurpleSavedstatusActivate(status)

while True:
  fortune = subprocess.Popen('fortune', stdout = subprocess.PIPE).stdout.read()
  set_status(fortune)
  time.sleep(120)
#-------------------------------

Start Pidgin and give following command:
$ python pidgin_status_message.py &

Playing Directory in Mplayer

2009-01-13T17:53:00.001+05:30

In order to play media files inside a directory with mplayer, I have written a shell script. Please save it in a directory in your $PATH variable.

For example, ~/bin/mplayer_dir.sh

#!/bin/bash

# Plays files inside a directory with mplayer

playlist="/home/mitesh/.mplayer/playlist.txt"

dir="./"
if [[ $# > 0 ]]
then
dir=$1
fi

#rm -f $playlist
find "$dir" -iname "*" | egrep -i "\.(wma|wmv|flv|mp3|avi|vob|dat|mp4|m4v|ogg|divx|xvid|rmvb|rm|asf)$" | sort > $playlist
#cat $playlist
nlines=`wc -l $playlist | awk '{print $1}'`

if [[ $nlines > 0 ]]
then
mplayer -playlist $playlist
else
echo "$0: Unrecognized files in $dir"
echo "Please update this script if playable format is present."

--------------

Sample Run:

$ mplayer_dir.sh [directory]

Ping Every Host in /etc/hosts File.

2008-11-28T12:52:00.002+05:30

If you want to know whether hosts specified in /etc/hosts file are reachable, just give the following command:

$ awk '/^[0-9]/{print $1}' /etc/hosts | xargs -l ping -c 1 $1

Sample run:

$ awk '/^[0-9]/{print $1}' /etc/hosts | xargs -l ping -c 1 $1
PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data.
64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.046 ms

--- 127.0.0.1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.046/0.046/0.046/0.000 ms
PING 127.0.1.1 (127.0.1.1) 56(84) bytes of data.
64 bytes from 127.0.1.1: icmp_seq=1 ttl=64 time=0.028 ms

--- 127.0.1.1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.028/0.028/0.028/0.000 ms

Missing Linux Entry in GRUB Menu

2008-11-07T13:22:00.002+05:30

If any Linux entry is not present in GRUB menu,
you can visit following forum to view a solution.

Linux Forum: Unable to see Fedora 7 in GRUB Menu

Finding Best Linux Distribution

2008-11-05T14:32:00.002+05:30

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

2008-11-04T13:58:00.002+05:30

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

2008-10-17T15:10:00.002+05:30

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

2008-10-16T15:40:00.002+05:30

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

2008-10-15T13:00:00.002+05:30

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

2008-10-13T15:18:00.013+05:30

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

$ ps aux | grep pattern
Copy the pid of the process from output of above command.
Paste this pid in the following command
$ 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

2008-10-03T16:49:00.002+05:30

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

Listing the Last Times a User Logged In

2008-10-03T16:39:00.002+05:30

To output a list of top 10 recent system users:

$ last | head

To output a list of last 10 logins of a user (say: mitesh):

$ last mitesh | head

Note: This command is very useful in determining who has
logged in the system at particular moment. Helpful in forensics ;)

Viewing PDF Files on Terminal

2008-10-01T15:30:00.002+05:30

First you need to convert a PDF document to HTML, then you run it through the elinks pager. There's a fine utility for doing just that, and it's called (appropriately) pdftohtml. You can find the home page for pdftohtml. If pdftohtml isn't already installed in your distribution of Linux, or isn't on your CD set, it's commonly available for Debian and RPM-based distributions, such as Fedora, SUSE, and more. The elinks program is also easily available if it isn't automatically installed in your distribution.
For example, you can install pdftohtml and elinks in Debian Linux with this command:
# apt-get install pdftohtml elinks

Users of the yum package can get the RPM version with this command:
# yum -y install pdftohtml elinks

Now you can view a PDF document with the following command. This particular command has one drawback. The output will not include frames (PDF files generally have a frame on the left that lets you jump to different pages).

$ pdftohtml -q -noframes -stdout document .pdf | elinks

If you want the left frame of page numbers, you can always use the following command instead:

$ pdftohtml -q document .pdf ; elinks document .html

You can write a script to save you all this typing each time you view a document. Use sudo or log in as root to create the /usr/local/bin/viewpdf script and enter the following code:

#!/bin/bash

pdftohtml -q $1 ~/temp.html
elinks ~/temp.html

#
#end of script

This code assumes it's OK to store the temporary HTML file in your home directory. You can use another location if you prefer. Now save your work and make the file executable:

$ sudo chmod +x /usr/local/bin/viewpdf

Create your own personalized boot splash backgrounds for GRUB

2008-10-01T14:03:00.004+05:30

The default GRUB bootloader screen is rather bland, but you can spice it up a little by creating your own custom graphical background screen for the bootloader.
GRUB imposes a number of limitations on the image size and number of colors. It also doesn't let you move the menu. The menu appears in a rectangle near the top of the screen, with some text instructions below the menu. This makes it relatively easy to create a graphical background screen for the GRUB bootloader, because you can focus primarily on making the bottom one-third of the screen interesting. That is not to say you cannot use other areas of the screen, but you should be careful. For example, don't make it difficult to read the GRUB instructions by placing complex graphics behind the text.

Here are the rather strict requirements for the image:

It must be sized at 640x480.
It must be a .xpm format image file (gzip compression is optional).
It must contain no more than 14 colors.Most people will cringe at the 14-color limit, but it is rather amazing what you can do with just 14 colors. Cartoon images are quite suitable for this narrow range of colors, and the narrow range of colors to represent the official Linux penguin (Tux) works fine.Find or create any image you want to try as a background for GRUB.

If you create an image yourself, it's best to create a 640x480 image and use as few colors as possible so that you don't lose the fidelity of the image when you later reduce it to 14 colors. Don't worry about using your graphics editor to limit yourself to 14 colors, however. It is possible to use the Gimp to reduce your image to use 14 colors, which can be a good way of fine-tuning the results you want.
Here is what you need:
A graphics editor, such as the Gimp, if you want to create or modify an image.
You must install ImageMagick if it is not already installed. Nearly all Linux distributions provide this on the install CD, and you can use your preferred package manager to install it.Suppose you have found or created the image myimage.png.
If you have ImageMagick installed, all you need to do to prepare the image is log in as root and issue these commands:

# convert myimage.png -colors 14 -resize 640x480 myimage.xpm

The convert command recognizes the extension png and knows what format it must convert the image from. It also recognizes the extension xpm and knows what format to convert the image to. The -colors 14 switch reduces the number of colors in the image to 14. If the image isn't already sized at 640x480, the switch -resize 640x480 will do that for you.

This is sample myimage.xpm

Changing RunLevel in Linux

2008-10-01T13:54:00.003+05:30

When a Linux system is booted, the first process that the kernel starts is /sbin/init. It is always process id (PID) 1 and has a parent process id (PPID) of 0. The init process is always running.
The /etc/inittab file is the configuration file for /sbin/init. /etc/inittab identifies the processes that init starts, and it can be customized as desired. Few environment variables are set when a process is started by init.
The inittab lines have four colon-separated fields:

id:runlevel:action:command

Let's look at the meaning of each.
(i). id The inittab id consists of one to four characters that identify the inittab line. The id must be unique.
(ii). runlevels The runlevels field contains one or more characters, usually numbers identifying the runlevels for which this process is started.

0 System Halt
1 Single user mode
2 Local multiuser without remote network (e.g., NFS)
3 Multiuser with network
4 Not used
5 Multiuser with network and xdm
6 System reboot

You can change runlevel by changing this field, to the number
you want. And reboot the machine.

How to find out which process is listening upon a port?

2008-09-17T17:26:00.001+05:30

How to find out which process is listening upon a port (say 6000) ?

$ lsof -i :6000

Alternatively, you can use following command:

$ fuser -v -n tcp 6000

Find Command : A Swiss Army Knife

2008-09-17T17:12:00.003+05:30

Find is a very useful and powerful utility. It is often used by system administration and in shell scripts. Here are 6 commands that might be useful:

$ find / -perm -4000 -print

This command will find every file on the system that is suid. This means that when you run it you will be running it as an other user. For example, traceroute is a utility that needs to be run as root. To allow users to run it, systems administrators will set it suid root so it will be run as root even if a user starts it. This can be useful, but can also be a big security risk if the utility has a security hole in it.

Here is another interesting command:

$ find / -atime +10 -print

This command will find all the files accessed more than 10 days ago. Commands like this one can be useful to find old files that need to be backuped or erased.

Find links that point to nothing

$ find / -type l -print | perl -nle '-e || print';

List zero-length files

$ find . -empty -exec ls {} \;

Finding files which contains a given pattern:

$ find . -type f -exec grep "pattern" /dev/null {} \;

Finding large files (>= 100 MB) in your home directory:

$find ~/ -size +100M

Creating Bootable USB from System Rescue CD

2008-09-06T19:17:00.000+05:30

Creating Bootable USB from System Rescue CD

In order to create bootable USB stick from CD image (ISO file)
of System Rescue Linux, generally we follow steps given
in this link. After following instructions given, I have created
a small shell script to create bootable rescue USB.

The contents of the script create_rescue_usb.sh are:
$ cat create_rescue_usb.sh
#!/bin/bash

if [[ $# < 4 ]]

then
  echo "Usage: $0 CDROM_Device CDROM_mount USB_Device USB_mount"
  exit
fi

CDROM_Device=$1
CDROM_mount=$2
USB_Device=$3
USB_mount=$4

if [[ -e $CDROM_Device ]]
then
  echo "$CDROM_Device is present."
else
  echo "$0: $CDROM_Device is not present."
  exit
fi

if [[ -e $USB_Device ]]
then
  echo "$USB_Device is present."
else
  echo "$0: $USB_Device is not present."
  exit
fi

echo "Mounting..."
mount -o loop $CDROM_Device $CDROM_mount

if [ $? -ne 0 ]
then
  echo "$0: cannot mount $CDROM_Device on $CDROM_mount."
  exit
fi

mount $USB_Device $USB_mount

if [ $? -ne 0 ]
then
  echo "$0: cannot mount $USB_Device on $USB_mount."
  umount $CDROM_mount
  exit
fi

echo "Copying Files..."
cp $CDROM_mount/syslinux/syslinux.cfg $USB_mount/
cp -r $CDROM_mount/isolinux/* $USB_mount/
cp -r $CDROM_mount/bootdisk/* $USB_mount/
cp $CDROM_mount/sysrcd.dat $USB_mount/

echo "Unmounting..."
umount $USB_mount
umount $CDROM_mount

echo "Making $USB_Device bootable..."
syslinux $USB_Device
sync

echo "$USB_Device is now ready to serve as bootable Linux USB."
#end of script

Now, you can make it executable.
$ chmod u+x create_rescue_usb.sh

Sample execution of above script (Please run as root user):
# ./create_rescue_cd.sh /path/of/system-rescue-cd.iso /mnt/cdrom /dev/sdb /mnt/usb

Where,
a. /path/of/system-rescue-cd.iso -- ISO image of the CD can be created as given in blog Creation of ISO Image of CD/DVD.
b. /mnt/cdrom -- directory, where you want to mount above ISO.
c. /dev/sdb -- or /dev/sdb1, your usb-stick device. May differ
according to your system configuration
d. /mnt/usb -- directory, where you want to mount usb-stick.

Now, your usb stick is ready to serve as bootable rescue USB.
You can test it. At the time of BIOS boot, please select USB device
as first boot device in BIOS. then save and reboot with the usb-stick
plugged in one USB port.

How to Download mms:// (MultiMedia Stream) Video?

2008-08-27T18:01:00.004+05:30

If you are not able to download the mms://a-web-site/stream_video.wmv
and only able to play via streaming. But you might have slow speed,

Then, you can use mencoder to download above file.

$ mencoder -oac copy -ovc copy -o out_video_file.wmv mms://a-web-site/stream_video.wmv

PS. If you want to view via streaming, you can use mplayer:

$ mplayer mms://a-web-site/stream_video.wmv

Denial of Service (DoS) Prevention

2008-08-22T12:14:00.002+05:30

You can prevent DoS on you machine, by running following
commands as root user. Or you can put following lines
in a shell script and run it as root.

# shut some DoS stuff down
echo 1 > /proc/sys/net/ipv4/tcp_syncookies
echo 1 > /proc/sys/net/ipv4/icmp_ignore_bogus_error_responses
echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts

# increase the local port range
echo 1024 65535 > /proc/sys/net/ipv4/ip_local_port_range

# increase the SYN backlog queue
echo 2048 > /proc/sys/net/ipv4/tcp_max_syn_backlog

echo 0 > /proc/sys/net/ipv4/tcp_sack
echo 0 > /proc/sys/net/ipv4/tcp_timestamps

How to stop certain network to start at boot time in Fedora?

2008-08-06T10:33:00.002+05:30

For example, if you do not want wlan0 to be started at boot time,
just move ifcfg-wlan0 file from /etc/sysconfig/network-scripts/ directory
to any other directory.

I am telling not to remove the file, because you can start
wlan0 interface after copying the file back to /etc/sysconfig/network-scripts/
whenever you want. And give command

# service network restart

Fixing tsocks 1.8 Beta

2008-08-01T11:05:00.005+05:30

I was trying to use tsocks 1.8 beta5 on Fedora 8. After installing
I was able to use it. But, on next day, what I found is: I was not
able to access any website, messenger service. Although, I was
able to ping websites. Then I realized the tsocks is interfering
with direct connection to Internet. I was not using ssh tunnel at
that moment.

I have created patch for Makefile and tsocks script.

$ vi patch_Makefile

5c5

< prefix=/usr

---

> prefix=/usr/local

9c9

< libdir = /lib

---

> libdir = ${prefix}/lib

31c31

< CFLAGS = -g -O2 -Wall

---

> CFLAGS = -O3 -Wall

$ vi patch_tsocks
6c6

< # /usr/bin/tsocks program [program arguments...]

---

> # $PREFIX/bin/tsocks program [program arguments...]

13c13

< # /usr/bin/tsocks telnet www.foo.org

---

> # $PREFIX/bin/tsocks telnet www.foo.org

20c20

< # . /usr/bin/tsocks on

---

> # . $PREFIX/bin/tsocks on

22c22

< # . /usr/bin/tsocks off

---

> # . $PREFIX/bin/tsocks off

26c26

< # source /usr/bin/tsocks on

---

> # source $PREFIX/bin/tsocks on

28c28

< # source /usr/bin/tsocks off

---

> # source $PREFIX/bin/tsocks off

33c33

< # /usr/bin/tsocks

---

> # $PREFIX/bin/tsocks

39a40,41

> PREFIX="/usr/local"

>

49c51

< export LD_PRELOAD="/usr/lib/libtsocks.so"

---

> export LD_PRELOAD="$PREFIX/lib/libtsocks.so"

51,52c53,54

< echo $LD_PRELOAD | grep -q "/usr/lib/libtsocks\.so" || \

< export LD_PRELOAD="/usr/lib/libtsocks.so $LD_PRELOAD"

---

> echo $LD_PRELOAD | grep -q "$PREFIX/lib/libtsocks\.so" || \

> export LD_PRELOAD="$PREFIX/lib/libtsocks.so $LD_PRELOAD"

56c58

< export LD_PRELOAD=`echo -n $LD_PRELOAD | sed 's/\/usr\/lib\/libtsocks.so \?//'`

---

> export LD_PRELOAD=`echo -n $LD_PRELOAD | sed 's/\$PREFIX\/lib\/libtsocks.so \?//'`

71c73

< export LD_PRELOAD="/usr/lib/libtsocks.so"

---

> export LD_PRELOAD="$PREFIX/lib/libtsocks.so"

73,74c75,76

< echo $LD_PRELOAD | grep -q "/usr/lib/libtsocks\.so" || \

< export LD_PRELOAD="/usr/lib/libtsocks.so $LD_PRELOAD"

---

> echo $LD_PRELOAD | grep -q "$PREFIX/lib/libtsocks\.so" || \

> export LD_PRELOAD="$PREFIX/lib/libtsocks.so $LD_PRELOAD"

How to apply patch and install tsocks?

$ tar -zxvf tsocks-1.8beta5.tar.gz

$ cd tsocks-1.8

$ ./configure

$ patch Makefile < patch_Makefile

$ patch tsocks < patch_tsocks

$ make

$ sudo make install

PS: If you do not find patches working, please mail me
at mitesh[dot]singh[dot]jat[at]gmail[dot]com . I will
send both patches to you.

Finding the Largest and the Smallest File in a Directory

2008-07-28T17:47:00.000+05:30

1. In order to find 9 largest files in a directory (say /etc),
please give following command:
$ ls -lS /etc | head
total 2816
-rw-r--r-- 1 root root 600399 2008-07-28 10:11 prelink.cache
-rw-r--r-- 1 root root 362047 2007-04-18 14:10 services
-rw-r--r-- 1 root root 144190 2007-10-12 15:08 lynx.cfg
-rw-r--r-- 1 root root 122098 2008-07-25 10:47 ld.so.cache
-rw-r--r-- 1 root root 117276 2007-09-17 17:57 Muttrc
-rw-r--r-- 1 root root 114765 2007-10-11 01:28 gwen-public-ca.crt
-rw-r--r-- 1 root root 84649 2007-08-23 12:54 sensors.conf
-rw-r--r-- 1 root root 44990 2007-10-16 18:50 php.ini
-rw-r--r-- 1 root root 31274 2007-10-09 14:33 jwhois.conf

2. In order to find 9 smallest files in a directory (say /etc),
please give following command:
$ ls -lSr /etc | head
total 2816
-rw-r--r-- 1 root root 0 2007-08-03 06:09 odbc.ini
-rw-r--r-- 1 root root 0 2000-01-13 04:48 motd
-rw-r--r-- 1 root root 0 2000-01-13 04:48 exports
-rw-r--r-- 1 root root 0 2007-08-16 19:23 environment
-rw-rw-r-- 1 root disk 0 2007-08-22 17:15 dumpdates
-rw-r--r-- 1 root root 0 2007-09-24 19:28 cron.deny
-rw------- 1 root root 1 2007-10-05 17:41 at.deny
lrwxrwxrwx 1 root root 7 2008-07-18 03:26 rc -> rc.d/rc
lrwxrwxrwx 1 root root 10 2008-07-18 03:26 rc6.d -> rc.d/rc6.d

Installing Linux (Fedora 8) on Macbook Pro

2008-07-23T15:32:00.000+05:30

I was trying to install Linux on Macbook Pro along with Mac OS X, because
it has Intel Processor, Intel chipset on Motherboard
and Nvidia 8600 GT graphics card. I followed steps
given in Debian Wiki (Mainly upto rEFIt part) and
in Mactel (for remaining part).

I would like to suggest some tips regarding installation of
Fedora 8 along with Mac OS X on Macbook Pro.

Audio: Download the latest Linux kernel and compile it with Intel HD Audio drivers 82801H (ICH8 Family).
Video: Boot into new kernel, and install NVidia driver, restart X server by logging out and logging in.
Keyboard: Download pomme daemon, Compile and install it. Now Optical Drive Eject button will work.
Backlight: Even after installing pommed, I was seeing very bright screen. I was not able to stare at screen for more than a minute. Later, after some tweaking of /etc/pommed.conf , I was able to decrease the backlit. I changed init = -1 to init = 1, as shown below:

# nVidia GeForce 8600M GT backlight control (MacBook Pro v3 & v4)
lcd_nv8600mgt {
# initial backlight level [12] (0 - 15, -1 to disable)
init = 1
# step value (1 - 2)
step = 1
# backlight level when on battery [6] (1 - 15, 0 to disable)
on_batt = 6
}

PS: Everything else should work as given in Mactel site. Feel free to write
comments. If you have any doubt, mail me at mitesh[dot]singh[dot]jat[at]gmail[dot]com

What is Pseudo Terminal (PTY)?

2008-07-18T14:49:00.000+05:30

Honestly, I did not know about the Pseudo Terminal before facing a problem. I had overwritten /etc/fstab in Fedora 8. As a result, I was not able to open either Terminal or Konsole. The error, I was getting, was:

Not enough permission for PTY device.

Then, I searched Internet for PTY device, there I found the full form of PTY, which is Pseudo Terminal.

Like the /dev directory, /dev/pts contains entries corresponding to devices. But unlike /dev, which is an ordinary directory, /dev/pts is a special directory that is created dynamically by the Linux kernel.The contents of the directory vary with time and reflect the state of the running system.

The entries in /dev/pts correspond to pseudo-terminals (or pseudo-TTYs, or PTYs). Linux creates a PTY for every new terminal window you open and displays a corresponding entry in /dev/pts.The PTY device acts like a terminal device—it accepts input from the keyboard and displays text output from the programs that run in it. PTYs are numbered, and the PTY number is the name of the corresponding entry in /dev/pts.

Then, I searched for how to open Pseudo Terminal with enough permissions.

Solution: Since I had overwritten the /etc/fstab, the entry to
mount devpts was not present. I then created the following entry in /etc/fstab file.

# file_system mount_point type options dump pass
none /dev/pts devpts (rw,mode=620) 0 0

Password-less SSH for Batch Processing

2008-07-10T12:25:00.000+05:30

1. Generation of Public-Private RSA key pair.

$ mkdir -p ~/.ssh
$ cd ~/.ssh
$ ssh-keygen -f keyname-identity -P '' -t rsa1


2. Allowing Password less Login on remote-machine.

Copy your public key on remote-machine.
$ scp keyname-identity.pub remote-machine:./.ssh/authorized_keys

Edit authorized_keys on remote-machine
Please place this line before your public key
in the authorized_keys file content
from="local_machine",no-pty,no-port-forwarding,no-X11-forwarding,no-agent-forwarding,command="remote_command_you_want_to_execute_on_local-machine"

For example:

from="local-machine",no-pty,no-port-forwarding,no-X11-forwarding,no-agent-forwarding,command="ls -la" 2048 35 1383...

3. Please make your private key secure.

$ chmod 511 ~/.ssh
$ chmod 400 ~/.ssh/keyname-identity

!! Caution !!

Putting a password less key in a file is exactly like writing a password on a piece of paper. A person who can access to your key file can do whatever you can do with the key.

Creation of ISO Image of CD/DVD

2008-07-08T15:36:00.000+05:30

If you want to create ISO image of CD/DVD in the
optical drive, please give the following command:

$ dd if=/dev/hdc of=/path/of/iso/image/xyz.iso

You can replace /dev/hdc (for Secondary Master)
with the CD/DVD drive path on your system. like

/dev/hdb (for Primary Slave)
/dev/sdc (for SATA optical drive,
or newer drive naming convention)

Most CPU Using Processes

2008-07-01T13:16:00.000+05:30

The following 1 line script prints the processes which are using CPU most of the time:

$ top -d 3600 -n 24 | awk '{arr[$13] += $10} END { for (x in arr) print x" \t"arr[x]; }' | sort -r -n -k2 > daily_stats

You can vary value of -d ---- and -n -- of top, to increase accuracy of
statistics. i.e. (delay) * (count) should be 86400 always for daily
statistics.
for example:

$ top -d 1800 -n 48 | awk '{arr[$13] += $10} END { for (x in arr) print x" \t"arr[x]; }' | sort -r -n -k2 > daily_stats

Bandwidth Limiting SCP (Secure CoPy)

2008-06-26T17:13:00.000+05:30

You can also limit the bandwidth scp may use when copying.
This is very useful if you want to copy a huge amount of data
without suffering from slow network for a long time. Limiting
bandwidth is done in this way:

$ scp -l bandwidthlimit_in_kbps username@remote_host:/path/to/file .

The bandwidth is specified in Kbit/sec. What does this mean?
Eight bits is one byte. If you want to copy no faster than
10 Kbyte/sec, set the limit to 80. If you want to copy no faster
than 80 Kbyte/sec, set the limit to 640. You should set the limit
to eight times the maximum Kbyte/sec you want it to be.
I would recommend to set the -l option with all scp'ing you do
on a connection that other people need to use, too. A big amount
of copying can virtually block a whole 10 Mbit network if you are
using hubs.

Reducing Booting Time in Linux

2008-06-24T17:28:00.000+05:30

You can reduce the booting time in Linux, by disabling the
services, which are not being used by you.

There is a directory for each run-level in /etc. Those
are named as /etc/rc.< run-level > , where
run-level = 0~6

On most Linux distros, default run-level is 5, in Debian default
run-level is 2.

1. Go to your run-level directory /etc/rc.n

# cd /etc/rc.5

2. If you want to disable, Apache Web-Server (apache), just
you have to rename, the corresponding file my replacing 'S'
(start) by 'K' (kill).

# mv S91apache K91apache

Likewise, you can disable all the undesired services.
This procedure will make your linux not only fast,
but also secure.

Prevention of Man-in-Middle Attack

2008-06-16T12:49:00.001+05:30

Having anticipated, Man-in-Middle attack by ARP Spoofing. a problem,
(For example: there are many lab machines which have NFS access to user
disks on a server. These machines may even be turned OFF which makes it
easy for a spoofer to get in.), I wrote a short Perl script designed to
be run from the system startup file.  Basically, it fills the ARP cache
on Linux with the IP and MAC addresses of known machines, setting a flag
so that they are never removed from the cache and can never be changed.

The config file format is simple -- IP address followed by MAC address,
separated by whitespace.  Pound at the beginning of a line indicates
comment.
For example:
# vi ip_mac.conf
# IP_Address MAC_Address
10.1.1.2 aa.bb.cc.dd.ee.ff
...
...


This has only been tested on Linux -- people on other platforms may need
to adjust the parameters to arp in the system call.

It is a quick 'n' dirty program, but works -- maybe it will be useful to
somebody out there, too.

Note: you want to make sure that it is run after your network interface is
brought up but before any servers or clients are started; otherwise,
somebody may be able to sneak in a connection before the ARP tables are
"locked".

Here is the Perl script:

# vi force_hw_addr.pl

#!/usr/bin/perl -w
# Program: force_hw_addr.pl
# Program to run ARP to force certain tables.

# Specify filenames(Redirection) or stdin

foreach (<>)    # For each input line....
{                 
 chomp;                        # Strip if CR/LF
 if (/^#/)
 {
   next;
 }           # If it's a comment, skip it.
if (((($host, $hw) = /\s*(.+?)\s+(\S+)\s*/) == 2) &&
     !(/^#/))
 {
 # The text between the slashes parses the input line as follows:
     # Ignore leading whitespace.  (\s*)
     # Then, start matching and put it into $host ($host, (.+?))
     # Skip over the whitespace after that (\s+)
     # Start matching.  Continue matching until end of line or optional
     # trailing whitespace.

     # Then, the if checks to see that both a
     # host and a hardware address were matched.
     # (2 matches).  If not, we skip the
     # line (assuming it is blank or invalid or something).
     # The second part of the if checks to see if the line starts with
     # a pound sign; if so, ignore it (as a comment).

     # Otherwise, run the appropriate command:
   printf("Setting IP %-15s to hardware address %s\n", $host, $hw);
   system "/usr/sbin/arp -s $host $hw\n";
 }
}

Example execution.

# ./force_hw_addr.pl < ip_mac.conf

I hope that this script will help you access resources in
your network and prevent DoS/Man-in-Middle Attack.

Process Status of Any Process Containing given String

2008-06-10T15:00:00.000+05:30

In order to get Process Status (ps) of any process containing given string
(say 'mitesh'), we use to type following commands, which are long and
tedious to type.

$ ps auxww | grep "mitesh" | grep -v grep

Instead, if we type

$ psg.sh mitesh

which is more convenient to type. So what this 'psg.sh'
contains (I am assuming, that ~/bin is in $PATH):

$ vi ~/bin/psg.sh

#!/bin/bash
function is ()
{
ps auxww | grep "$@" | grep -v "grep"
}

is $@

# END : psg.sh

Ethernet Configurations on Fedora/RHEL

2008-06-10T12:51:00.000+05:30

In order to configure ethernet (Usually eth0 for first ethernet card),
open /etc/sysconfig/network-scripts/ifcfg-eth0 file.

# vi /etc/sysconfig/network-scripts/ifcfg-eth0

#!/bin/sh

#>>>Device type: ethernet
#>>>Variable declarations:
DEVICE=eth0
IPADDR=192.168.0.2
NETMASK=255.255.255.0
NETWORK=192.168.0.0
BROADCAST=255.255.255.255
GATEWAY=192.168.0.1

# Whether to make available after boot
# or enable at root's consent
ONBOOT=no

# PROTO = dhcp, none

#>>>End variable declarations

Booting in Single User Mode in Linux

2008-06-10T12:39:00.000+05:30

At the boot time, you usually see GRUB (GRand Unified Boot) Loader.

You select any one option of available OSs from the menu.

For example, if you have Windows and Linux.
You will get 2(or more) options to boot.

In order to boot into single user mode, you select desired
linux and press 'e' in grub menu, you will see new window
with something given below

root (hd0,0)
kernel /boot/vmlinuz-2.6.22.6 root=/dev/sda1 ro resume=/dev/sda3
initrd /boot/initrd.img-2.6.22.6
savedefault

Now, you append '1' or 'single' in the second line (kernel) as kernel
parameter. For example

kernel /boot/vmlinuz-2.6.22.6 root=/dev/sda1 ro resume=/dev/sda3 1

or

kernel /boot/vmlinuz-2.6.22.6 root=/dev/sda1 ro resume=/dev/sda3 single

Now, press 'b', to boot into single user mode. :)

Shortcuts for Working in BASH (Bourne Again SHell)

2008-06-09T09:19:00.000+05:30

Navigation
Left/right cursor key --- Move left/right in text
Ctrl+A --- Move to beginning of lIne
Ctrl+E --- Move to end of line
Ctrl+right arrow --- Move forward one word
Ctrl+left arrow --- Move left one word

Editing
Ctrl+U --- Delete everything behind cursor to start of line
Ctrl+K --- Delete from cursor to end of line
Ctrl+W --- Delete from cursor to beginning of word
Alt+D --- Delete from cursor to end of word
Ctrl+T --- Transpose characters on left and right of cursor
Alt+T --- Transpose words on left and right of cursor

Miscellaneous
Ctrl+L --- Clear screen (everything above current line)
Ctrl+U --- Undo everything since last command
Alt+R --- Undo changes made to the line
Ctrl+Y --- Undo deletion of word or line caused by using Ctrl+K, Ctrl+W, and so on
Alt+L --- Lowercase current word (from the cursor to end of word)

Note: If you find these shortcuts hard to remember and you know vi(m),
you can enable vi mode for editing command line using following command:

$ set -o vi

To enable vi mode from start of Bash, add following lines to your ~/.bashrc
# Start vi Mode for command line editing
set -o vi