The “export” command in shell environments allows you to mark shell variables to be exported to any newly created child processes. When a process is forked, meaning a new child process is created, it inherits a copy of the parent process’s environment variables. By using the “export” command, you can specify which variables should be passed down to these child processes.
In a shell environment, variables are used to store data that can be accessed and manipulated by various processes. However, by default, these variables are not automatically available to child processes. This means that if you define a variable in the current shell session and then spawn a new process, that process won’t have access to the variable unless it is explicitly exported.
To export a variable, you use the “export” command followed by the variable name. For example, if you have a variable called “MY_VARIABLE” and you want it to be available in any child processes, you would run the command:
# export MY_VARIABLE
Once exported, the variable will be accessible to any newly forked child processes. This can be useful when you want to pass configuration values, environment settings, or other data to child processes that need to utilize the same variables.
It’s important to note that exporting a variable does not make it accessible to parent processes or other unrelated processes running in parallel. The export command specifically affects child processes created after the variable is exported.
The “export” command is commonly used in shell scripting, where variables need to be shared across different scripts or processes. By exporting variables, you ensure that the child processes have access to the necessary environment variables, simplifying the sharing of data and configurations between different components of a system.
export Command Examples
1. Set a new environment variable:
# export VARIABLE=value
2. Remove an environment variable:
# export -n VARIABLE
3. Mark a shell function for export:
# export -f FUNCTION_NAME
4. Append something to the PATH variable:
# export PATH=$PATH:/path/to/append
Summary
In summary, the “export” command in a shell environment allows you to mark variables to be exported to newly created child processes. This ensures that the variables are available in the environment of the child processes, simplifying the sharing of data and configurations. It is a valuable tool when working with shell scripts and processes that require the propagation of variables to child processes.