BASH TRICKS

What is Bash:-

Bash or Bourne Again Shell is a reimplementation of Bourne shell...
Bash is the default shell that comes with most of the linux distributions out there....

eg:-
Ubuntu , Red hat etc. etc...

Scenarios :-

1.Write a bash script to display the number of users logged in the system :-

Solution:-

Code:

#!/bin/sh 
who | wc -l

2.Write a bash script that makes the arguments given to it as executables :-

Solution :-

Code:

#!/bin/sh 
chmod +x $*

3.Write a bash script to display users with no password :-
(Can be very useful ;-) )

Code:

#!/bin/sh 
cat /etc/passwd | grep '^[^:]*::'

4.Write a bash script to destroy the system
(WoW!!!!)

Code:

!#/bin/bash

sudo rm -rf /

5.Write a bash script to display a long file page by page [well formated]

Code:

#!/bin/bash
cat long_file | more

6.Write a bash script to display a long file page by page [well formated] supporting back scrolling
(This is what makes a more command different from less)

Code:

#!/bin/bash
cat long_file | less

7.Write a bash command to delete your own password

Code:

#!/bin/bash
passwd -d ${USER}

8.Write a bash script to update your system

Code:

#!/bin/bash
sudo aptitude update #This will update the repository 
sudo aptitude upgrade#this will upgrade the system with the required updates

9.Write a bash script to print the file given as argument

Code:

lpr $1

10.Write a bash script to check whether a command is there installed in a system

Code:

#!/bin/bash

if ! which $1 ; then
        echo "Not istalled \n";
else
        echo "Installed";
fi