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.\" Converted into a manpage again by Martin Schulze <joey@infodrom.org>
.\"
.\" Added -lutil remark, 030718
.\"
-.TH OPENPTY 3 "2003-07-18" "BSD" "Linux Programmer's Manual"
+.TH OPENPTY 3 2017-09-15 "GNU" "Linux Programmer's Manual"
.SH NAME
-openpty, login_tty, forkpty \- tty utility functions
+openpty, login_tty, forkpty \- terminal utility functions
.SH SYNOPSIS
+.nf
.B #include <pty.h>
-\ /* for openpty and forkpty */
-.br
+.PP
+.BI "int openpty(int *" amaster ", int *" aslave ", char *" name ,
+.BI " const struct termios *" termp ,
+.BI " const struct winsize *" winp );
+.PP
+.BI "pid_t forkpty(int *" amaster ", char *" name ,
+.BI " const struct termios *" termp ,
+.BI " const struct winsize *" winp );
+
.B #include <utmp.h>
-/* for login_tty */
-.sp
-.BI "int openpty(int *" amaster ", int *" aslave ", char *" name ", struct termios *" termp ", struct winsize * " winp );
-.sp
+.PP
.BI "int login_tty(int " fd );
-.sp
-.BI "pid_t forkpty(int *" amaster ", char *" name ", struct termios *" termp ", struct winsize *" winp );
-.sp
-Link with \-lutil.
+.PP
+Link with \fI\-lutil\fP.
+.fi
.SH DESCRIPTION
The
-.B openpty()
-function finds an available pseudo-terminal and returns file descriptors
+.BR openpty ()
+function finds an available pseudoterminal and returns file descriptors
for the master and slave in
.I amaster
and
.I winp
is not NULL, the window size of the slave will be set to the values in
.IR winp .
-
+.PP
The
-.B login_tty()
-function prepares for a login on the tty
+.BR login_tty ()
+function prepares for a login on the terminal
.I fd
-(which may be a real tty device, or the slave of a pseudo-terminal as
+(which may be a real terminal device, or the slave of a pseudoterminal as
returned by
-.BR openpty() )
+.BR openpty ())
by creating a new session, making
.I fd
-the controlling terminal for the current process, setting
+the controlling terminal for the calling process, setting
.I fd
to be the standard input, output, and error streams of the current
process, and closing
.IR fd .
-
+.PP
The
-.B forkpty()
+.BR forkpty ()
function combines
-.BR openpty() ,
-.BR fork() ,
+.BR openpty (),
+.BR fork (2),
and
-.B login_tty()
-to create a new process operating in a pseudo-terminal. The file
-descriptor of the master side of the pseudo-terminal is returned in
-.IR amaster ,
-and the filename of the slave in
+.BR login_tty ()
+to create a new process operating in a pseudoterminal.
+The file
+descriptor of the master side of the pseudoterminal is returned in
+.IR amaster .
+If
.I name
-if it is not NULL. The
+is not NULL, the buffer it points to is used to return the
+filename of the slave.
+The
.I termp
and
.I winp
-parameters, if not NULL,
+arguments, if not NULL,
will determine the terminal attributes and window size of the slave
-side of the pseudo-terminal.
-.SH "RETURN VALUES"
+side of the pseudoterminal.
+.SH RETURN VALUE
If a call to
-.BR openpty() ,
-.BR login_tty() ,
+.BR openpty (),
+.BR login_tty (),
or
-.B forkpty()
+.BR forkpty ()
is not successful, \-1 is returned and
.I errno
-is set to indicate the error. Otherwise,
-.BR openpty() ,
-.BR login_tty() ,
+is set to indicate the error.
+Otherwise,
+.BR openpty (),
+.BR login_tty (),
and the child process of
-.B forkpty()
+.BR forkpty ()
return 0, and the parent process of
-.B forkpty()
+.BR forkpty ()
returns the process ID of the child process.
.SH ERRORS
-.B openpty()
-will fail if:
+.BR openpty ()
+fails if:
.TP
.B ENOENT
-There are no available ttys.
-.LP
-.B login_pty()
-will fail if
-.B ioctl()
+There are no available terminals.
+.PP
+.BR login_tty ()
+fails if
+.BR ioctl (2)
fails to set
.I fd
-to the controlling terminal of the current process.
-.LP
-.B forkpty()
-will fail if either
-.B openpty()
+to the controlling terminal of the calling process.
+.PP
+.BR forkpty ()
+fails if either
+.BR openpty ()
or
-.B fork()
+.BR fork (2)
fails.
-.SH NOTE
-These functions are included in libutil, hence you'll need to add
-.B \-lutil
-to your compiler command line.
-.SH FILES
-.I /dev/[pt]ty[pqrstuwxyzabcdePQRST][0123456789abcdef]
-.SH "CONFORMING TO"
-These are BSD functions, present in libc5 and glibc2.
+.SH ATTRIBUTES
+For an explanation of the terms used in this section, see
+.BR attributes (7).
+.TS
+allbox;
+lbw20 lb lb
+l l l.
+Interface Attribute Value
+T{
+.BR forkpty (),
+.BR openpty ()
+T} Thread safety MT-Safe locale
+T{
+.BR login_tty ()
+T} Thread safety MT-Unsafe race:ttyname
+.TE
+.sp 1
+.SH CONFORMING TO
+These are BSD functions, present in glibc.
+They are not standardized in POSIX.
+.SH NOTES
+The
+.B const
+modifiers were added to the structure pointer arguments of
+.BR openpty ()
+and
+.BR forkpty ()
+in glibc 2.8.
+.PP
+In versions of glibc before 2.0.92,
+.BR openpty ()
+returns file descriptors for a BSD pseudoterminal pair;
+since glibc 2.0.92,
+it first attempts to open a UNIX 98 pseudoterminal pair,
+and falls back to opening a BSD pseudoterminal pair if that fails.
.SH BUGS
Nobody knows how much space should be reserved for
.IR name .
So, calling
-.B openpty()
+.BR openpty ()
or
-.B forkpty()
+.BR forkpty ()
with non-NULL
.I name
may not be secure.
-.SH "SEE ALSO"
-.BR fork (2)
+.SH SEE ALSO
+.BR fork (2),
+.BR ttyname (3),
+.BR pty (7)
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