Exit in Chapel

Here’s an idiomatic Chapel code example demonstrating the concept of program exit:

use IO;
use OS;

proc main() {
  // This writeln will not be executed due to the exit call
  defer writeln("This will not be printed!");

  // Exit the program with status code 3
  exit(3);
}

This Chapel program demonstrates how to exit a program with a specific status code. Let’s break it down:

1. We use the IO module for input/output operations and the OS module for system-related functions like exit().

2. The main() procedure is the entry point of our Chapel program.

3. We use a defer statement to schedule a writeln() call that should be executed when the procedure exits normally. However, this will not be printed due to the exit() call.

4. The exit(3) call immediately terminates the program with a status code of 3.

To run this program:

1. Save the code in a file named exit_example.chpl.
2. Compile and run the program using the Chapel compiler:

$ chpl exit_example.chpl -o exit_example
$ ./exit_example

You won’t see any output because the program exits before printing anything.

To check the exit status:

$ echo $?
3

This will display the exit status of the last executed command, which in this case is 3.

Important notes:

• Unlike some other languages, Chapel doesn’t use the return value from main() to set the exit status. Instead, you should use the exit() function to explicitly set a non-zero exit status.
• The defer statement in Chapel is similar to Go’s defer, but it’s important to note that deferred actions are not executed when using exit().
• Chapel’s exit() function is part of the OS module, which provides various system-level operations.

This example showcases how to properly exit a Chapel program with a specific status code, which can be useful for indicating success or failure to the calling environment.