Variables in Linux Shell Script

By: Vivek G. Viewed: 153354 times  Printer Friendly Format    


To process our data/information, data must be kept in computers RAM memory. RAM memory is divided into small locations, and each location had unique number called memory location/address, which is used to hold our data. Programmer can give a unique name to this memory location/address called memory variable or variable (Its a named storage location that may take different values, but only one at a time).

In Linux (Shell), there are two types of variable:
(1) System variables - Created and maintained by Linux itself. This type of variable defined in CAPITAL LETTERS.
(2) User defined variables (UDV) - Created and maintained by user. This type of variable defined in lower letters.

You can see system variables by giving command like $ set, some of the important System variables are:

System Variable
Meaning
BASH=/bin/bash Our shell name
BASH_VERSION=1.14.7(1) Our shell version name
COLUMNS=80 No. of columns for our screen
HOME=/home/vivek Our home directory
LINES=25 No. of columns for our screen
LOGNAME=students students Our logging name
OSTYPE=Linux Our Os type
PATH=/usr/bin:/sbin:/bin:/usr/sbin Our path settings
PS1=[\u@\h \W]\$ Our prompt settings
PWD=/home/students/Common Our current working directory
SHELL=/bin/bash Our shell name
USERNAME=vivek User name who is currently login to this PC

NOTE that Some of the above settings can be different in your PC/Linux environment. You can print any of the above variables contains as follows:
$ echo $USERNAME
$ echo $HOME



Most Viewed Articles (in Linux )

Latest Articles (in Linux)

smskannel SMS gateway run in background

Running jar files in background in ssh window

Could not open '': No such file or directory at lib/ExtUtils/MM_Unix.pm line 2697

Can't locate ExtUtils/MakeMaker.pm in @INC ...

bash: make: command not found

apxs: command not found

bash: svn: command not found

make: Nothing to be done for `all'.

How to burn your CD / DVD ISO image using Media Creator (Adaptec/Roxio) on Windows

How to burn your CD / DVD ISO image using Nero Burning ROM (Ahead Software) on Windows

How to burn your CD / DVD ISO image using Nero Express (Ahead Software) on Windows

How to burn your CD / DVD ISO image using NISO Recorder V2 Power Toy on Windows

How to burn your CD / DVD ISO image using k3b on CentOS

Compiling and Installing software from source in Linux

Installing RPM's using the Redhat Package Manager in Linux

Comment on this tutorial