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.Dd January 2, 2022 .Dt PTSNAME 3 .Os .Sh NAME .Nm ptsname , .Nm ptsname_r .Nd get the pathname of the slave pseudo-terminal device .Sh LIBRARY .Lb libc .Sh SYNOPSIS n stdlib.h .Ft char * .Fn ptsname "int masterfd" .Ft int .Fn ptsname_r "int masterfd" "char *buf" "size_t buflen" .Sh DESCRIPTION The .Fn ptsname function returns the pathname of the slave pseudo-terminal device that corresponds to the master pseudo-terminal device associated with .Fa masterfd . The .Fn ptsname function is not reentrant or thread-safe.
p The .Fn ptsname_r function places the pathname of the slave pseudo-terminal device that corresponds to the master pseudo-terminal device associated with .Fa masterfd int the .Fa buf argument copying up to .Fa buflen characters. The .Fa buf is always .Dv NUL terminated. .Sh RETURN VALUES If successful, .Fn ptsname returns a pointer to a nul-terminated string containing the pathname of the slave pseudo-terminal device. If an error occurs .Fn ptsname will return .Dv NULL and .Va errno is set to indicate the error.
p If successful, .Fn ptsname_r places a nul-terminated string containing the pathname of the slave pseudo-terminal device in .Fa buf and returns .Dv 0 . If an error occurs .Fn ptsname_r will return an error number indicating what went wrong. .Sh ERRORS The .Fn ptsname and .Fn ptsname_r functions will fail if: l -tag -width Er t Bq Er EACCESS the corresponding pseudo-terminal device could not be accessed. t Bq Er EBADF .Fa masterfd is not a valid descriptor. t Bq Er EINVAL .Fa masterfd is not associated with a master pseudo-terminal device. .El
p In addition the .Fn ptsname_r function will return: l -tag -width Er t Bq Er EINVAL the .Fa buf argument is .Dv NULL . t Bq Er ERANGE the name of the pseudo-terminal is longer than .Fa bufsiz characters plus the terminating .Dv NUL . .El .Sh NOTES The error returns of .Fn ptsname are a .Nx extension. The .Fn ptsname function is equivalent to: d -literal static struct ptmget pm; return ioctl(masterfd, TIOCPTSNAME, &pm) == -1 ? NULL : pm.sn; .Ed
p Both the .Fn ptsname and .Fn ptsname_r functions will also return the name of the slave pseudo-terminal if a file descriptor to the slave pseudo-terminal is passed to .Fa masterfd .
p This is a convenient extension because it allows one to use the file descriptor obtained by .Xr open 2
a /dev/tty to obtain the name of the pseudo-terminal for the current process. .Sh SEE ALSO .Xr ioctl 2 , .Xr open 2 , .Xr grantpt 3 , .Xr posix_openpt 3 , .Xr unlockpt 3 .Sh STANDARDS The .Fn ptsname function conforms to .St -p1003.1-2001 . Its first release was in .St -xpg4.2 .
Indexes created Sun Oct 05 05:09:57 GMT 2025