1.\" $NetBSD: openpty.3,v 1.14 2008/11/28 07:17:17 dholland Exp $ 2.\" 3.\" Copyright (c) 1995 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" This code is derived from software developed by the Computer Systems 7.\" Engineering group at Lawrence Berkeley Laboratory under DARPA contract 8.\" BG 91-66 and contributed to Berkeley. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 3. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.Dd November 28, 2008 35.Dt OPENPTY 3 36.Os 37.Sh NAME 38.Nm openpty , 39.Nm login_tty , 40.Nm forkpty 41.Nd tty utility functions 42.Sh LIBRARY 43.Lb libutil 44.Sh SYNOPSIS 45.In util.h 46.Ft int 47.Fn openpty "int *amaster" "int *aslave" "char *name" "struct termios *termp" "struct winsize *winp" 48.Ft int 49.Fn login_tty "int fd" 50.Ft pid_t 51.Fn forkpty "int *amaster" "char *name" "struct termios *termp" "struct winsize *winp" 52.Sh DESCRIPTION 53The 54.Fn openpty , 55.Fn login_tty , 56and 57.Fn forkpty 58functions perform manipulations on ttys and pseudo-ttys. 59.Pp 60The 61.Fn openpty 62function finds an available pseudo-tty and returns file descriptors 63for the master and slave in 64.Fa amaster 65and 66.Fa aslave . 67If 68.Fa name 69is non-null, the filename of the slave is returned in 70.Fa name . 71If 72.Fa termp 73is non-null, the terminal parameters of the slave will be set to the 74values in 75.Fa termp . 76If 77.Fa winp 78is non-null, the window size of the slave will be set to the values in 79.Fa winp . 80.Pp 81The 82.Fn login_tty 83function prepares for a login on the tty 84.Fa fd 85(which may be a real tty device, or the slave of a pseudo-tty as 86returned by 87.Fn openpty ) 88by creating a new session, making 89.Fa fd 90the controlling terminal for the current process, setting 91.Fa fd 92to be the standard input, output, and error streams of the current 93process, and closing 94.Fa fd . 95.Pp 96The 97.Fn forkpty 98function combines 99.Fn openpty , 100.Fn fork , 101and 102.Fn login_tty 103to create a new process operating in a pseudo-tty. 104The file descriptor of the master side of the pseudo-tty is returned 105(to the parent process only) in 106.Fa amaster . 107The filename of the slave is returned (to both the parent and child 108processes) in 109.Fa name 110if 111.Fa name 112is non-null. 113The 114.Fa termp 115and 116.Fa winp 117parameters, if non-null, will determine the terminal attributes and 118window size of the slave side of the pseudo-tty. 119.Sh RETURN VALUES 120If a call to 121.Fn openpty , 122.Fn login_tty , 123or 124.Fn forkpty 125is not successful, -1 is returned and 126.Va errno 127is set to indicate the error. 128Otherwise, 129.Fn openpty , 130.Fn login_tty , 131and the child process of 132.Fn forkpty 133return 0, and the parent process of 134.Fn forkpty 135returns the process ID of the child process. 136.Sh FILES 137.Bl -tag -width /dev/[pt]ty[p-zP-T][0-9a-zA-Z] -compact 138.It Pa /dev/[pt]ty[p-zP-T][0-9a-zA-Z] 139.El 140.Sh ERRORS 141.Fn openpty 142will fail if: 143.Bl -tag -width Er 144.It Bq Er ENOENT 145There are no available ttys. 146.It Bq Er EPERM 147The caller was not the superuser and the 148.Xr ptm 4 149device is missing or not configured. 150.El 151.Pp 152.Fn login_tty 153will fail if 154.Fn ioctl 155fails to set 156.Fa fd 157to the controlling terminal of the current process. 158.Fn forkpty 159will fail if either 160.Fn openpty 161or 162.Fn fork 163fails. 164.Sh SEE ALSO 165.Xr fork 2 166