Consider these important facts:
- Environment variables are all upper case.
- To use their values, precede the name with a
$
.
Linux utilizes Bash as the default shell and when a session started it reads commands from ~/.bash_profile
.
Environment variables are set in the file ~/.bashrc
.
📝 Note: The files ~/.bash_profile
and .bashrc
are hidden. To list hidden files, type ls -a
.
Here is a list of some common environment variables:
$HOME
- Path of your home directory$PATH
- List of directories where the system checks for programs to run$LD_LIBRARY_PATH
- List of directories where the system checks for shared libraries to load$HOSTNAME
- The name of the host, e.g.tigris.doane.edu
.
📝 Note: See the values of all your environment variables by typing env
on your terminal.
-
Display the value of an environment variable using
echo
:echo $HOME /home/UID
-
Modify the value of environment variables with
export
:export PATH=$PATH:/home/UID export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/home/UID/custom_lib_directory
-
Set a value for environment variables:
export OMP_NUM_THREADS=12
This command sets the value of the variable called OMP_NUM_THREADS (an OpenMP parameter) to 12.