LINUX ENVIRONMENT VARIABLES
In Linux environment variables are variables that are set in the shell session and can be accessed by all processes and programs that are executed within that session. Environment variables are used to store information that can be used by programs and scripts to customize their behavior or to provide configuration data.
Here are some commonly used environment variables in Linux:
PATH - contains a list of directories where executable files are located.
HOME - points to the current user's home directory.
USER - stores the username of the current user.
PWD - stores the current working directory.
LANG - specifies the default language and localization settings for the system.
TERM - specifies the type of terminal being used. You can view the list of environment variables by using the printenv command or by typing env in the terminal. To set an environment variable, you can use the export command followed by the variable name and its value. For example, to set the MY_VAR variable to "Hello, World!", you can run the following command:
arduino
Copy code
export MY_VAR="Hello, World!"
To make the environment variable permanent, you can add the export command to your shell's configuration file (e.g., ~/.bashrc for the Bash shell).
SCOPE OF AN ENVIRONMENT VARIABLE IN LINUX:
In Linux, environment variables are variables that contain information about the system's environment, such as the current user, the path to the system's directories, and the default settings for various programs. The scope of an environment variable in Linux depends on how and where it is set.
Global scope: Environment variables that are set in the system-wide configuration files, such as /etc/profile, /etc/bashrc, or /etc/environment, are available to all users and processes on the system.
User scope: Environment variables that are set in a user's shell configuration files, such as ~/.bashrc or ~/.profile, are available only to that user's processes and any child processes they spawn.
Process scope: Environment variables that are set in the context of a specific process, such as by using the export command in a shell script, are available only to that process and any child processes it spawns.
It's important to note that environment variables set in a child process are not automatically available to the parent process or any other processes running on the system. However, some programs may provide mechanisms for passing environment variables between processes, such as command-line arguments or configuration files.
In summary, the scope of an environment variable in Linux depends on where and how it is set, with options for system-wide, user-specific, and process-specific settings.
HOW DOES LINUX ENVIRONMENT VARIABLES COMMAND WORK:
In Linux, environment variables are variables that contain information about the system's environment, such as the current user, the path to the system's directories, and the default settings for various programs. There are several ways to work with environment variables in Linux, including setting, displaying, and deleting them using command-line tools.
Setting environment variables: To set an environment variable, you can use the export command followed by the variable name and value, separated by an equal sign. For example, to set the PATH variable to include the directory /usr/local/bin, you can use the command:
bash
Copy code
export PATH=/usr/local/bin:$PATH
This command adds the /usr/local/bin directory to the beginning of the PATH variable, which is a colon-separated list of directories that the shell uses to search for executable files.
Displaying environment variables: To display the value of an environment variable, you can use the echo command followed by the variable name, enclosed in curly braces {}. For example, to display the value of the PATH variable, you can use the command:
bash
Copy code
echo ${PATH}
This command prints the value of the PATH variable to the console.
Deleting environment variables: To delete an environment variable, you can use the unset command followed by the variable name. For example, to delete the PATH variable, you can use the command:
bash
Copy code
unset PATH
This command removes the PATH variable from the shell's environment.
It's important to note that environment variables are case-sensitive in Linux, and their values can contain spaces and other special characters if they are enclosed in quotes. Also, environment variables set in one shell session are not automatically available in other sessions or when the system is restarted, so you may need to add them to your shell's startup files to make them persistent.
