Environment Variables

What are environment variables in UNIX operating system. How to use them.Someone kindly give a example also.

Environment variable - as the name suggests - is the variable that resides in Unix System Environment.
This variable - once dfefined- can be accessed by any script/program/application which runs in the unix box.

For example let us say we have a dedicated FTP location to which we need all report files to be sent. We can declare FTP_HOME as an environment variable and use this as $FTP_HOME inside any script which runs in the UNIX box.

cheers,
Kalayama

Can one change the value of the Environment Variable after it is defined.I do not have idea on this and what to know about this. Someone help me!!

Definitely the value of the environment variable can be changed after it is defined.

- Kalayama

[QUOTE=nehalshah;4384]What are environment variables in UNIX operating system. How to use them.Someone kindly give a example also.[/QUOTE]

Environmental variables global variables which can used all subshells.
they r defined using command

$export Global_Variable="value"

now this Global_Variable can be used in all sub shell which u run in the same terminal.