Environment Variables

The way that environment variables are set under unix depends on which shell you are using. You can confirm which shell by entering :

echo $SHELL

Listing Current Variables

To see what is currently set within your current shell, simply enter :

env

and a list of settings is displayed.

Single Variable

To view the value of a single variable - MYVAR - enter :

echo $MYVAR

Case Sensitive

Unlike the DOS derived Windows environments, environment variables are case sensitive. If unsure of the case of a specific variable, you can combine the env command with grep like this :

env | grep -i myvar

Setting Variables In Current Environment

Some different shell syntaxes are shown :

csh, tsh

setenv SOME_VAR "some value"
setenv NEW_VAR "$OLD_VAR"

bash

export SOME_VAR "some value"
export NEW_VAR $OLD_VAR

korn

SOME_VAR = "some value";export SOME_VAR
NEW_VAR = $OLD_VAR;export NEW_VAR

Setting Permanent System-Wide Variables

To set a variable for all shell environments you should edit the /etc/profile file.

Alternatively you can modify the shell specific initialization files such as : .cshrc, .tcshrc or .bshrc.

Delimiter

On Unix the character ':' (colon) is conventionally used to delimit lists of values set against an environment variable. The ';' (semi-colon) delimits separate commands, allowing them to be arranged on the same line.

Executing Command Files

You need to ensure two things :

• The command can be found - either directly on the PATH or executed from its own directory and the current directory is on the PATH.

• The file must be executable, if in doubt enter : chmod +x <file>