ptsname, ptsname_r — get the name of the slave pseudoterminal
#define _XOPEN_SOURCE /* See feature_test_macros(7) */ #include <stdlib.h>
| char
            *ptsname( | int fd ); | 
#define _GNU_SOURCE /* See feature_test_macros(7) */ #include <stdlib.h>
| int
            ptsname_r( | int fd, | 
| char *buf, | |
| size_t buflen ); | 
The ptsname() function
      returns the name of the slave pseudoterminal device
      corresponding to the master referred to by fd.
The ptsname_r() function is
      the reentrant equivalent of ptsname(). It returns the name of the slave
      pseudoterminal device as a null-terminated string in the
      buffer pointed to by buf. The buflen argument specifies the
      number of bytes available in buf.
On success, ptsname()
      returns a pointer to a string in static storage which will be
      overwritten by subsequent calls. This pointer must not be
      freed. On failure, a NULL pointer is returned.
On success, ptsname_r()
      returns 0. On failure, a nonzero value is returned and
      errno is set to indicate the
      error.
(ptsname_r() only)
            buf is
            NULL.
fd does not
            refer to a pseudoterminal master device.
(ptsname_r() only)
            buf is too
            small.
ptsname() is part of the
      UNIX 98 pseudoterminal support (see pts(4)). This function is
      specified in POSIX.1-2001.
ptsname_r() is a Linux
      extension. A version of this function is documented on Tru64
      and HP-UX, but on those implementations, −1 is returned
      on error, with errno set to
      indicate the error. Avoid using this function in portable
      programs.