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Learn how to correctly format file names with variables in KSH scripts to prevent errors and improve readability.
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This video is based on the question https://stackoverflow.com/q/67507654/ asked by the user 'Configueroa' ( https://stackoverflow.com/u/2280760/ ) and on the answer https://stackoverflow.com/a/67507945/ provided by the user 'mao' ( https://stackoverflow.com/u/8290634/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Dynamically Include Variables in a File Name in KSH Scripts

Programming and scripting are full of challenges, and one such challenge arises when you want to include variables in a file name within your shell scripts. If you've ever struggled with getting the right output while echoing constructed filenames in KornShell (ksh), you are not alone! This guide will help you understand one common mistake and how to properly format your code for success.

The Problem

You might encounter the following scenario in your KSH scripting endeavors. Suppose you want to create a filename that includes dynamically generated elements: a loop counter and the current date. However, when you run your script, you receive unexpected output that looks like this:

[[See Video to Reveal this Text or Code Snippet]]

This output shows that the variable $FILE is not correctly evaluated, which leads to confusion. It's essential to determine how to include variables effectively in your filename.

Example Code That Causes Confusion

Here’s an example script that faces this issue:

[[See Video to Reveal this Text or Code Snippet]]

Issues in the Above Script

Variable Assignment - There is an unnecessary space around the equals sign in FILE, which causes KSH to treat it differently.

Echoing Variables – The way variables are echoed without the right formatting results in them being displayed literally instead of their values.

The Solution

The solution is relatively simple: use the ${...} syntax to clearly define and include your variables. This not only enhances readability but also ensures accurate variable interpolation. Moreover, using proper indentation can significantly improve the clarity and maintainability of your code.

Here’s the Corrected Version of the Script

Let’s rewrite the initial example to fix these problems:

[[See Video to Reveal this Text or Code Snippet]]

Key Changes Made

Removed space around the equals sign for variable assignment: FILE="/lsf10/monitors/lpstat_email_${i}_vmobius_${today}.txt" ensures that the variable is assigned correctly.

Used ${} syntax: By enclosing the variable names in curly braces, echo now correctly interprets the varable values rather than display their names as text.

Improved Indentation: Clear indentation makes your code easier to read and understand for anyone who may look at it later.

Conclusion

Including variables in file names in your KSH scripts can seem tricky at first, but with the right syntax and attention to detail, you can avoid common pitfalls. Remember to use ${...} for variable interpolation, and keep your scripts well-indented for better readability. By following these tips, you'll set yourself up for success in your shell scripting endeavors! Happy scripting!