Bad substitution error when running iso.sh with sh

[dfaw20]

Thanks.

When executing the script iso.sh using bash (i.e., bash iso.sh), it completes successfully. However, running the same script with sh (i.e., sh iso.sh) results in a Bad substitution error. This issue seems to stem from sh not supporting certain syntax that is specific to bash, specifically the substring extraction and manipulation within the script. It's important for iso.sh to be accessible and user-friendly, even to those not familiar with shell scripting nuances, as users might attempt to run a .sh file with sh and give up if they encounter errors.

Steps to Reproduce

Create a script named iso.sh with the following content:

#!/bin/bash
flavour="vanilla"
flavourcap=`echo ${flavour:0:1} | tr '[a-z]' '[A-Z]'`${flavour:1}
echo $flavourcap

Make the script executable: chmod +x iso.sh Run the script with bash: bash iso.sh Run the script with sh: sh iso.sh

Expected Behavior

The script should run successfully with both bash and sh, printing "Vanilla" to the console.

Actual Behavior

When run with bash, the script succeeds and prints "Vanilla". When run with sh, the script fails with the following error message:

iso.sh: line 3: Bad substitution

Environment

Operating System: Ubuntu 22.04.4 LTS Bash version: 5.1.16

Additional Context

This issue appears to be related to the use of bash-specific features not supported in sh, particularly the use of substring manipulation. For users not deeply familiar with shell scripting, this could lead to confusion and frustration, potentially causing them to give up on using iso.sh.

Proposed Solutions

There are two main approaches to resolving this issue:

Enhance Documentation: Clearly specify in the release notes and execution instructions that iso.sh should be run with bash (i.e., bash iso.sh). This approach provides immediate clarity to the user but does not address the underlying compatibility issue.

Modify the Script: Since the issue arises from a non-core logic portion of the script, consider rewriting this part to be compatible with sh. This would involve avoiding bash-specific syntax and features to ensure the script can be executed successfully in both bash and sh environments. This solution enhances the script's accessibility and usability across different shells, making it more beginner-friendly.

[AdityaGarg8]

If you have ideas, feel free to open a PR.

[dfaw20]

@AdityaGarg8 Thanks. I opened a PR #110 .

[AdityaGarg8]

I've merged the PR. Make sure it runs on macOS as well.