Weird Effects When One CMD Script Runs Another, from Inside a Function

Have you ever encountered strange behavior when running one CMD script from another script, especially when they are called from inside a function? This article will explore some of the weird effects that can occur and provide explanations for these unexpected behaviors.

When one CMD script runs another, it is common to use the CALL command followed by the name of the script. This allows the second script to be executed and then control is returned to the first script. However, things can get a bit tricky when this happens inside a function.

Let's delve into some of the weird effects that can occur:

1. Variables Not Being Set or Preserved

One common issue is that variables set in the first script may not be accessible in the second script when called from inside a function. This happens because the second script runs in a separate instance of the CMD interpreter, and any variables set in the first script are not automatically passed to the second script.

To overcome this, you can pass the variables as arguments to the second script using the %* syntax, which represents all the arguments passed to the script. For example:

Inside the second script, you can access the passed arguments using the %* syntax. This ensures that the variables are properly set and preserved.

2. Exiting the Parent Script

When a second script is called from inside a function, it can sometimes exit the parent script unexpectedly. This happens because the EXIT command in the second script terminates the entire script, including the parent script.

To prevent this, you can use the GOTO command to jump to a label instead of using EXIT. For example:

This ensures that only the second script is terminated, and the parent script continues executing as expected.

3. Delayed Expansion Issues

Delayed expansion is a feature in CMD that allows variables to be expanded at execution time rather than at parse time. However, when a second script is called from inside a function, delayed expansion can behave unexpectedly.

One common issue is that variables inside the second script may not be expanded correctly. This happens because the second script is executed in a separate instance of the CMD interpreter, and the delayed expansion settings are not automatically inherited.

To resolve this, you can enable delayed expansion explicitly in the second script by using the SETLOCAL EnableDelayedExpansion command. This ensures that variables are expanded correctly.

4. Working Directory Changes

Another weird effect that can occur is a change in the working directory when a second script is called from inside a function. The working directory may be different from what you expect, which can cause issues when accessing files or executing commands.

To overcome this, you can use the CD command to change the working directory explicitly to the desired location before calling the second script. For example:

This ensures that the working directory is set correctly before executing the second script.

By understanding and addressing these weird effects, you can avoid unexpected behaviors when running one CMD script from another, especially from inside a function. Remember to pass variables as arguments, use GOTO instead of EXIT, enable delayed expansion explicitly, and set the working directory appropriately.

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