c/io/perror

Prints a textual description of the error code currently stored in the system variable errno to stderr.

The description is formed by concatenating the following components:
 * the contents of the null-terminated byte string pointed to by, followed by (unless  is a null pointer or the character pointed to by  is the null character)
 * implementation-defined error message string describing the error code stored in, followed by . The error message string is identical to the result of.

Return value
(none)