Linux Basics

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Environment variables

Unix shell provides environment variables. These variables are used to control the functionality of our whole environment (systemwide) and not only to the current shell. The one restricted only to a particular shell are called shell variables.

To see the entire list of environment variables, use:


These environment variables can be used by the shell, programs or commands.

For example, the $PS1 variable is used by the shell to display the prompt. To change your prompt, you can try:

PS1='MyPrompt: '

Please note that if you change your prompt it might make you uncomfortable but you can execute any commands as usual. Here is the snapshot of me executing pwd and whoami commands from new prompt.

bash-4.2$ OLDP=$PS1
bash-4.2$ PS1='MyPrompt: '
MyPrompt: pwd
MyPrompt: whoami

To restore back to the previous prompt, try:


There are many other environment variables with various utilities. For example, the environment variable $PATH is a list of directories separated by a colon. It is used by the shell to find the file corresponding to a command.

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