#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-termi-
       nated 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.

       EINVAL (ptsname_r() only) buf is NULL.

       ENOTTY fd does not refer to a pseudoterminal master device.

       ERANGE (ptsname_r() only) buf is too small.

       ptsname() is provided in glibc since version 2.1.

   Multithreading (see pthreads(7))
       The ptsname() function is not thread-safe.

       The ptsname_r() function is thread-safe.

       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 docu-
       mented on Tru64 and HP-UX, but on those implementations, -1 is returned
       on error, with errno set to indicate the error.  Avoid using this func-
       tion in portable programs.
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