Gd_error_string report a getdata library error
#include <getdata.h> char *gd_error_string(const DIRFILE *dirfile, char *buffer, size_t buflen);
The gd_error_string() function returns a string describing the last dirfile error encountered while operating on dirfile.
If buffer is not NULL, the string is written to this memory location. At most buflen characters will be written. This always includes a terminating null byte, even if the error string was truncated. The numeric dirfile error itself may be obtained by calling gd_error(3).
If buffer is NULL, gd_error_string() will allocate a string of sufficient length using malloc(3), and buflen is ignored. In this case, the caller should deallocate the returned string using free(3) when it is no longer needed.
The dirfile argument should point to a DIRFILE object previously created by a call to gd_open(3).
If buffer is non-NULL, the gd_error_string() function returns buffer, or NULL if buflen is less than one. Otherwise, it returns a newly malloc'd string of sufficient length which should be deallocated by the caller. The error state of dirfile is unchanged.