ptsname(3) Library Functions Manual ptsname(3)

ptsname, ptsname_r - get the name of the slave pseudoterminal

Standard C library (libc, -lc)

#include <stdlib.h>
char *ptsname(int fd);
int ptsname_r(int fd, char buf[.buflen], size_t buflen);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):


    Since glibc 2.24:
        _XOPEN_SOURCE >= 500
    glibc 2.23 and earlier:



The ptsname() function returns the name of the slave pseudoterminal device corresponding to the master referred to by the file descriptor 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, NULL is returned.

On success, ptsname_r() returns 0. On failure, an error number is returned to indicate the error.

(ptsname_r() only) buf is NULL. (This error is returned only for glibc 2.25 and earlier.)
fd does not refer to a pseudoterminal master device.
(ptsname_r() only) buf is too small.

For an explanation of the terms used in this section, see attributes(7).

Interface Attribute Value
ptsname () Thread safety MT-Unsafe race:ptsname
ptsname_r () Thread safety MT-Safe

A version of ptsname_r() 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.


ptsname_r() is a Linux extension, that is proposed for inclusion in the next major revision of POSIX.1 (Issue 8).

POSIX.1-2001. glibc 2.1.

ptsname() is part of the UNIX 98 pseudoterminal support (see pts(4)).

grantpt(3), posix_openpt(3), ttyname(3), unlockpt(3), pts(4), pty(7)

2024-05-02 Linux man-pages 6.9.1