While we may all be familiar with executing scripts, how does it compare to sourcing scripts? I have sourced scripts before but didn't really bother really digging into the differences. Let's get into it.

Visual representation of the difference

  • executing
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    # this executes the script in the current directory
    # must be executable
    $ ./script

    # this executes the script if located in some directory in $PATH
    # must be executable
    $ script

  • sourcing 
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    # this sources the script
    # does NOT have to be executable
    $ source script

    # also sources the script and need NOT be executable
    # does exactly the same thing as `source script` because bash defines `source` as an alias to the dot
    $ . script

Verbal representation of the difference

  • Executing
    • Runs all the commands in a new/separate shell.
    • Any changes to the environment as a result of the commands only apply to the new shell. This means the environment in the current shell remains untouched.
  • Sourcing
    • Runs all the commands in the current shell.
    • Any changes to the environment resulting from the commands will apply in the current shell.

References

What is the difference between executing a Bash script vs sourcing it?