Sending stderr (Standard Error) to Pipe

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

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

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

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

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."

fi

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

Sample Run:

$ mplayer_dir.sh [directory]

Ping Every Host in /etc/hosts File.

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

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