man pages section 3: Basic Library Functions

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Updated: July 2014



ttyname, ttyname_r - find pathname of a terminal


#include <unistd.h> 

char *ttyname(int fildes);
char *ttyname_r(int fildes, char *name, int namelen);

Standard conforming

cc [ flag...] file ... –D_POSIX_PTHREAD_SEMANTICS [ library ... ]

int ttyname_r(int fildes, char *name, size_t namesize);


The ttyname() function returns a pointer to a string containing the null-terminated path name of the terminal device associated with file descriptor fildes. The return value points to thread–specific data whose content is overwritten by each call from the same thread.

The ttyname_r() function has the same functionality as ttyname() except that the caller must supply a buffer name with length namelen to store the result; this buffer must be at least _POSIX_PATH_MAX in size (defined in <limits.h>). The standard-conforming version (see standards(5)) of ttyname_r() takes a namesize parameter of type size_t.

Return Values

Upon successful completion, ttyname() and ttyname_r() return a pointer to a string. Otherwise, a null pointer is returned and errno is set to indicate the error.

The standard-conforming ttyname_r() returns 0 if successful or the error number upon failure.


The ttyname() and ttyname_r() functions may fail if:


The fildes argument is not a valid file descriptor. This condition is reported.


The fildes argument does not refer to a terminal device. This condition is reported.

The ttyname_r() function may fail if:


The value of namesize is smaller than the length of the string to be returned including the terminating null character.


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

Interface Stability

See also

Intro(3), gettext(3C), setlocale(3C), attributes(5), standards(5)


When compiling multithreaded applications, see Intro(3), Notes On Multithreaded Applications.

Messages printed from this function are in the native language specified by the LC_MESSAGES locale category. See setlocale(3C).

The return value of ttyname() points to thread–specific data whose content is overwritten by each call from the same thread. This function is safe to use in multithreaded applications, but its use is discouraged. The ttyname_r() function should used instead.

Solaris 2.4 and earlier releases provided definitions of the ttyname_r() interface as specified in POSIX.1c Draft 6. The final POSIX.1c standard changed the interface as described above. Support for the Draft 6 interface is provided for compatibility only and might not be supported in future releases. New applications and libraries should use the standard-conforming interface.