What is the default exit value of a command and what does it signify?

• A. 0 — The command ran successfully.
• B. 1 — The command failed.
• C. 2 — The command ran with a partial success.
• D. 255 — The command terminated abnormally.

Answer: (A)

In Unix-like systems, a command reports an exit status to the shell when it finishes. The default exit value is zero, which means the command completed successfully without errors. Any non-zero value signals that something went wrong or a different condition occurred, but the exact meaning of those codes is determined by the program. The exit status range is 0 to 255, with 0 universally indicating success, while non-zero codes are used variably by different programs. You can see this in practice by inspecting the special variable that holds the last command’s status: a successful command yields 0, whereas a failing one yields a non-zero value. For example, a command that runs cleanly returns 0, while a failing command returns 1 or another non-zero code depending on the program.