Gawk/Updating-ERRNO

From Get docs

17.4.7 Updating ERRNO

The following functions allow you to update the ERRNO variable:

void update_ERRNO_int(int errno_val);
Set ERRNO to the string equivalent of the error code in errno_val. The value should be one of the defined error codes in <errno.h>, and gawk turns it into a (possibly translated) string using the C strerror() function.
void update_ERRNO_string(const char *string);
Set ERRNO directly to the string value of ERRNO. gawk makes a copy of the value of string.
void unset_ERRNO(void);
Unset ERRNO.