Resolving the source Command Issue in Bash Scripts

Learn why the `source` command behaves differently in a Bash script and how to fix it by upgrading Bash on your Mac.
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Fixing the source Command Not Working in Bash Scripts

If you've ever worked with Bash scripting, you may have encountered various command issues. One such problem arises when the source command doesn't behave as expected in scripts, especially on older versions of Bash. In this post, we will explore a common scenario that leads to this issue and provide a clear solution to get your scripts working correctly.

The Problem

Let’s consider a code snippet that works perfectly when input directly into the terminal:

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In this example, the source command correctly sets a variable ABC to 1, and the subsequent echo command prints this variable’s value.

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Running this script yields no output when it comes to the echo $ABC line. You might think that source is malfunctioning when, in fact, the underlying issue is related to the version of Bash being used.

The Underlying Cause: Bash Version

The Apple version of Bash that ships with macOS can be quite outdated. This particular behavior you've noticed stems from the fact that certain features present in more recent versions of Bash may not be available in the older versions.

Why It Matters

The process substitution syntax (<(...)) is not fully supported in earlier versions of Bash.

Older versions may lack enhancements and bug fixes that improve command compatibility and usability.

In your case, as confirmed during testing, your original command works seamlessly with Bash version 5.1.16, which is the version available from Homebrew.

Solution: Upgrade Bash

To rectify the issue, you need to upgrade your Bash version. Here’s how you can do it easily on a Mac:

Step-by-Step Guide to Upgrade Bash

Install Homebrew (if you haven't already):
Homebrew is a popular package manager for macOS. You can install it by running this command in your terminal:

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Upgrade Bash:
Once Homebrew is set up, install the latest Bash version by running:

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Change your default shell (if needed):
After installation, you may want to set the newer version as your default shell. You can do this by following these commands:

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Restart Terminal:
Close and reopen your terminal or reboot your system to ensure changes take effect.

Verify the Installation:
Check the current Bash version by typing:

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Now, with the updated version of Bash, your script should work just fine:

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Conclusion

In conclusion, if you encounter the source command not functioning correctly within a Bash script, the likely culprit is an outdated version of Bash on your system. By upgrading to the latest version via Homebrew, you can take advantage of the full range of Bash features, ensuring your scripts run smoothly. Don't let older software hold you back — keep your tools updated for optimal performance!