errstr.1s

errstr errno

errno
    The numerical error code to translate into a string. If omitted, defaults to 0.

The errstr command translates numerical error codes into human-readable error messages.
It takes a single numerical argument, which it interprets as an error number. It then looks up the corresponding error message in the system's error code table and prints the message to standard output. If no argument is provided, errstr assumes a value of zero.
The primary use case of errstr is in shell scripts or other programs where you need to convert an error number returned by a system call or other function into a user-friendly error message for reporting or logging purposes. This is especially helpful when the error number is not immediately obvious or when you want to provide a consistent and localized error reporting mechanism.
Because the meanings of error codes can be platform dependent, the output of errstr may vary across different operating systems.

The output of errstr depends on the system's error code table. Error message translations may vary or be incomplete across different systems.

Errstr returns 0 on success and non-zero when there is a usage error.

errstr 2 outputs No such file or directory on many systems (POSIX).

perror(3), errno(3)