Featured Post

Taking inputs from user in a script

Here we will see how to take input from user in a script with the help of read command. #!/bin/bash Lets try multiplication of two numbers which the user enters. What read does is ? It takes values by user on stdin. It prompt the user to input any value on stdin. -p is used to display a prompt. read -p "First number:" value1 This will give a prompt as " First number " and store the value in variable " value1 " echo Will display a blank line. read -p "Second number:" value2 This will give a prompt as " Second number " and store the value in variable " value2 " echo Will display a blank line. read -sn1 -p "Press any key to see the answer..." Just to make it bit more interactive lets add one more thing. -s means silent mode that is if any value is pressed it will not be displayed on the screen like as in the password. -nX means how many characters. X here is one that is any
Post a Comment

Introduction to Linux Shell

Shell is a program that takes commands from the keyboard and gives them to the operating system to perform actions accordingly.

Mostly Linux operating system has a application called Bash (aka Bourne Again SHell, which is an enhanced version of the original Bourne SHell.

There are several additional shell programs available on a Linux system such as ksh, csh, tcsh etc.

There are various "terminal emulators" available. Basically these are the programs that helps to interact with the shell. For instance xterm, konsole, gnome-terminal. You can get this launched via your utilities or programs menu.

Your terminal will look somewhat like given below:

[root@sunny-workstation ~]# 
or
[sunny@sunny-workstation ~]$ 

This means USER@HOSTNAME PWD followed by # or $ if you are logged in via root then it will show # otherwise for every normal user it will state $.

In above example root/sunny are the users, sunny-workstation is the hostname and ~ means their home directory.

Comments

Post a Comment

Popular posts from this blog

Merging of various commands

Lets create a file with following content: #!/bin/bash echo "Value which is there in variable USER  is $USER" What this above line will do, it will fetch the variable USER which is built-in. echo -e "-e is used to add new line $USER.\n" Adding -e will execute \n and will add a new line. name=$USER We also can assign the built-in variables to another variables as here value of $USER will be stored in name variable. echo -e "Assigning value of USER variable to another variable $name \n" shortname=$(cat /etc/passwd | grep "sunny" | awk -F ":" '{print $5}' | cut -d " " -f1) Here we are merging various commands. What above line will do is firstly it will cat the file /etc/passwd from that it will grep the line which has sunny. sunny :x:1000:1000:Sunny Bhambhani:/home/sunny:/bin/bash Then by the help of awk command it will get the 5th field which contains the full name of the user. Sunn
Read more

Positional parameters in Bash scripting

Here we will see the naming convention of parameters which are passed to a script and how we can use them? how shifting works? #!/bin/bash # Positional parameters #       $0          $1     $2    $3   .......   $n # Command  Arg1 Arg2 Arg3 ....... Argn echo -e "First argument $1, Second argument $2, Third argument $3, Fourth argument $4\n" This will print value of all four arguments which you passed, just for your reference. shift The positional parameters from n+1 ... are renamed  to  $1, so that every time after shift is performed there is a new argument to be processed. This will shift to the left by one value. echo "Shifting...." echo -e "First argument $1, second argument $2, third argument $3, fourth argument $4 \n" This will print new values after shifting the arguments by one value. shift 2 This will shift to the left by two values. echo "Shifting.... by 2 vlaues" echo -e "First argument $1, second
Read more

Sourcing a variable

Lets create a file with following content: #!/bin/bash echo "$var1" Assign a value to a local variable var1 sunny@sunny-workstation bin]$ var1=sunny-workstation sunny@sunny-workstation bin]$ chmod +x 2_simple_script.sh  When you will run this script it will state nothing. That's because script doesn't know anything about var1 variable and that it exists in shell environment. sunny@sunny-workstation bin]$ ./2_simple_script.sh  sunny@sunny-workstation bin]$ But if we source this script via . or source built-in command it will show the output as the script will run in the same environment as our shell sunny@sunny-workstation bin]$ . ./2_simple_script.sh  sunny-workstation sunny@sunny-workstation bin]$ source 2_simple_script.sh  sunny-workstation sunny@sunny-workstation bin]$
Read more