In the world of programming, exit codes are like cryptic messages from your programs. They tell you how a program ended, with 0 usually signifying success and higher numbers indicating errors.  One in particular, exit code 9, is considered by many to be untrappable.  What does this mean?  I'm so glad you asked.

Typically, a program can do error handling and/or logging and use its built-in exit() function to exit gracefully.  In some instances, a program might receive a signal like SIGKILL, a special message from the operating system to the program which forcefully closes the program and does not give it a chance to trap errors and exit gracefully.  Since the program did not set an exit code and exit gracefully, the operating system assigns it an exit code, commonly exit code 9.

There is no universally accepted "untrappable" exit code, though 9 is often associated with the underlying cause of the termination that results in the program not executing any final code, including that which would set any custom exit codes and trap the signal from the operating system.

The point of all this is to remember to push boundaries and strive to achieve that which others say is impossible.  Think outside the box and write code that overcomes obstacles and gets the job done.