#include <unistd.h>
char *ttyname(int fildes);
int ttyname_r(int fildes, char *name, size_t
namesize);
The ttyname() function shall return a pointer to a string containing a null-terminated pathname of the terminal associated with file descriptor fildes. The return value may point to static data whose content is overwritten by each call.
The ttyname() function need not be reentrant. A function that is not required to be reentrant is not required to be thread-safe.
The ttyname_r() function shall store the null-terminated pathname of the terminal associated with the file descriptor fildes in the character array referenced by name. The array is namesize characters long and should have space for the name and the terminating null character. The maximum length of the terminal name shall be {TTY_NAME_MAX}.
Upon successful completion, ttyname() shall return a pointer to a string. Otherwise, a null pointer shall be returned and errno set to indicate the error.
If successful, the ttyname_r() function shall return zero. Otherwise, an error number shall be returned to indicate the error.
The ttyname() function may fail if:
The ttyname_r() function may fail if:
The following sections are informative.
The term ``terminal'' is used instead of the historical term ``terminal device'' in order to avoid a reference to an undefined term.
The thread-safe version places the terminal name in a user-supplied buffer and returns a non-zero value if it fails. The non-thread-safe version may return the name in a static data area that may be overwritten by each call.
The Base Definitions volume of IEEE Std 1003.1-2001, <unistd.h>