1.\" $OpenBSD: openpty.3,v 1.17 2015/08/28 19:54:06 kettenis Exp $ 2.\" Copyright (c) 1995 3.\" The Regents of the University of California. All rights reserved. 4.\" 5.\" This code is derived from software developed by the Computer Systems 6.\" Engineering group at Lawrence Berkeley Laboratory under DARPA contract 7.\" BG 91-66 and contributed to Berkeley. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 3. Neither the name of the University nor the names of its contributors 18.\" may be used to endorse or promote products derived from this software 19.\" without specific prior written permission. 20.\" 21.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31.\" SUCH DAMAGE. 32.\" 33.Dd $Mdocdate: August 28 2015 $ 34.Dt OPENPTY 3 35.Os 36.Sh NAME 37.Nm openpty , 38.Nm login_tty , 39.Nm forkpty 40.Nd tty utility functions 41.Sh SYNOPSIS 42.In termios.h 43.In util.h 44.Ft int 45.Fn openpty "int *amaster" "int *aslave" "char *name" "struct termios *termp" "struct winsize *winp" 46.Ft int 47.Fn login_tty "int fd" 48.Ft pid_t 49.Fn forkpty "int *amaster" "char *name" "struct termios *termp" "struct winsize *winp" 50.Sh DESCRIPTION 51The 52.Fn openpty , 53.Fn login_tty , 54and 55.Fn forkpty 56functions perform manipulations on ttys and pseudo-ttys. 57.Pp 58The 59.Fn openpty 60function finds an available pseudo-tty and returns file descriptors 61for the master and slave in 62.Fa amaster 63and 64.Fa aslave . 65If 66.Fa name 67is non-null, the filename of the slave is returned in 68.Fa name 69(a string of at least 16 characters). 70If 71.Fa termp 72is non-null, the terminal parameters of the slave will be set to the 73values in 74.Fa termp . 75If 76.Fa winp 77is non-null, the window size of the slave will be set to the values in 78.Fa winp . 79.Pp 80The 81.Fn openpty 82function allocates the pseudo-tty through the 83.Pa /dev/ptm 84device (see 85.Xr pty 4 86for details) which means that its ownership is changed to the UID of 87the caller, permissions are set to correct values, and all earlier 88uses of that device are revoked (see 89.Xr revoke 2 90for details). 91.Pp 92The 93.Fn login_tty 94function prepares for a login on the tty 95.Fa fd 96(which may be a real tty device, or the slave of a pseudo-tty as 97returned by 98.Fn openpty ) 99by creating a new session, making 100.Fa fd 101the controlling terminal for the current process, setting 102.Fa fd 103to be the standard input, output, and error streams of the current 104process, and closing 105.Fa fd . 106.Pp 107The 108.Fn forkpty 109function combines 110.Fn openpty , 111.Fn fork , 112and 113.Fn login_tty 114to create a new process operating in a pseudo-tty. 115The file 116descriptor of the master side of the pseudo-tty is returned in 117.Fa amaster , 118and the filename of the slave in 119.Fa name 120if it is non-null. 121The 122.Fa termp 123and 124.Fa winp 125parameters, if non-null, will determine the terminal attributes and 126window size of the slave side of the pseudo-tty. 127.Sh RETURN VALUES 128If a call to 129.Fn openpty , 130.Fn login_tty , 131or 132.Fn forkpty 133is not successful, \-1 is returned and 134.Va errno 135is set to indicate the error. 136Otherwise, 137.Fn openpty , 138.Fn login_tty , 139and the child process of 140.Fn forkpty 141return 0, and the parent process of 142.Fn forkpty 143returns the process ID of the child process. 144.Sh FILES 145.Bl -tag -width /dev/tty[p-zP-T][0-9a-zA-Z]x -compact 146.It Pa /dev/pty[p-zP-T][0-9a-zA-Z] 147master pseudo terminals 148.It Pa /dev/tty[p-zP-T][0-9a-zA-Z] 149slave pseudo terminals 150.It Pa /dev/ptm 151pseudo terminal management device 152.El 153.Sh ERRORS 154.Fn openpty 155will fail if: 156.Bl -tag -width Er 157.It Bq Er ENOENT 158There are no available ttys. 159.El 160.Pp 161.Fn login_tty 162will fail if 163.Fn ioctl 164fails to set 165.Fa fd 166to the controlling terminal of the current process. 167.Fn forkpty 168will fail if either 169.Fn openpty 170or 171.Fn fork 172fails. 173.Sh SEE ALSO 174.Xr fork 2 , 175.Xr revoke 2 , 176.Xr pty 4 177