Debuggging bash cron scripts.

I have to several times debug scripts that I get complain about working when logging in normally but they do not work when run in cron mode. So, quite a lot of times, redirecting the stderr of the script is all that is required to see what is happening, but sometimes that just does not help if the script is calling another script which is mis-behaving and under lot of other conditions. So, how to at-least take a look at why these are failing, login with ssh.

bash debug – log all executed commands

Whenever I am writing a script in perl or bash, I always wish that there
was some way to have all the commands logged or output to screen. I know
there is “set -x” option to have debugging enabled, but sometimes that
seems to be too much information and I dont really need all that. So, here
is something I found recently for bash to log all the executed commands.

bash – using the vi mode more effectively.

You can first set the bash mode to vi. This will enable some vim like features to bash. So, add this to .bashrc :

set -o vi

Once, you have done that then its time to get more out of the vi mode. First, check some things and set some interesting stuff.

bashrc with lots of functions and useful alias

Here is a link of a useful 10K lines bashrc

http://pastebin.com/LEkXXuST

You may not want to put the whole thing, but get an idea and use what you think can be helpful to you or at-least get an idea. This was not posted by me, so if you are re-using code as is, check the permissions to copy.

poor mans watch, watch for solaris

Here is a simple script that you can use as watch in Solaris as well.

watch()
{
    #Poor man's watch
    while (true)
    do
        clear
        $*
        sleep 2;
    done
}

Disable a few cores when you want to save power.

If you have a lot of CPU power and working on battery. If you do not need that much of power and would like to rather save some battery power by disabling some cpus then you can use the below script. This script disables cpus from 4 to 7. You can change the number in the for loop. You would need the sudo to be setup or remove sudo and run the script as root. The script will show you the currently active cpu’s before and after disabling the CPU’s.

quick bash script for datewise backup of directory

I was working on something and the data was very critical and needed backup. I wrote a bash script to back up the data every 5 hours with cron and bash script. Thought I will share that with you. Here is the script.

#!/bin/bash - 
#===============================================================================
#
#          FILE:  backup.sh
# 
#         USAGE:  ./backup.sh 
# 
#   DESCRIPTION:  Backup all the current files.
# 
#       OPTIONS:  ---
#  REQUIREMENTS:  ---
#          BUGS:  ---
#         NOTES:  ---
#        AUTHOR: Amit Agarwal (aka), amit.agarwal@roamware.com
#       COMPANY: Roamware India Pvt Ltd
#       CREATED: 08/19/2011 02:43:32 PM IST
#      REVISION:  ---
#===============================================================================
backupf=( a b c d) #Here you need to specify the directory you need to backup.
bkupdir="/tmp/backup/$(date +%Y)/$(date +%m)/$(date +%d)" #Here you can change the basedir for the backups
mkdir  -p $bkupdir
sudo tar cvfz $bkupdir/bkup_$(date "+%Y%m%d_%H%M").tgz $backupf[*] #Remove sudo if you do not need it.
echo "Backup created in dir $dir"

And then just add it to cron as “00 */5 * * * /home//bin/backup.sh”. Change the path if it does not match what is given here.