The strerror() function maps the error number in errnum to an error message string, and returns a pointer to that string. It uses the same set of error messages as perror(3C). The returned string should not be overwritten.

The strerror() function returns the string "Unknown error" if errnum is out of range.

See attributes(5) for descriptions of the following attributes:

gettext(3C), perror(3C), setlocale(3C), attributes(5)

If the application is linked with -lintl, then messages returned from this function are in the native language specified by the LC_MESSAGES locale category; see setlocale(3C).