Export Command in Linux

Introduction

export command in Linux marks an environment variable to be exported with any newly forked child processes and thus it allows a child process to inherit all marked variables. Frequently Used Options

• -p : List of all names that are exported in the current shell
• -n : Remove names from export list
• -f : Names are exported as functions

Exported variables such as $HOME and $PATH are available to other programs run by the shell that exports them as environment variables. Regular (non-exported) variables are not available to other programs.

Example

Variable va is not defined and exported so grep will not show any result.

env | grep 'va='            # No environment variable called variable
va=Hello                    # Create local (non-exported) variable with value
env | grep 'va='            # Still no environment variable called variable

After exporting the variable using export command, it is available from the child process.

export va                # Mark variable for export to child processes
env | grep 'va='         # Output is 'va=Hello'

To remove this variable from the export list we need to use the -n export option.

export -n va

The most common use of the export command is when defining the PATH shell variable. In the example below, we have included additional path /usr/local/bin to the existing PATH definition.

export PATH=$PATH:/usr/local/bin

Exporting Shell function

With the option -f the export command can also be used to export functions. In the example below, we will create a function called print() and export it.

$ print () { echo "Hello"; }  # Define function
$ export -f printname         # Export function
$ bash                        # Bash shell
$ print                       # Output is 'Hello'

print function is accessible in the new bash shell created using bash command.