1.\" 2.\" Copyright (c) 1996 Joerg Wunsch 3.\" 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR 16.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, 19.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25.\" 26.\" $FreeBSD: src/lib/libutil/pty.3,v 1.8.2.3 2001/12/17 10:08:32 ru Exp $ 27.\" $DragonFly: src/lib/libutil/pty.3,v 1.3 2007/06/30 19:03:52 swildner Exp $ 28.\" " 29.Dd December 29, 1996 30.Os 31.Dt PTY 3 32.Sh NAME 33.Nm openpty , 34.Nm forkpty 35.Nd auxiliary functions to obtain a pseudo-terminal 36.Sh LIBRARY 37.Lb libutil 38.Sh SYNOPSIS 39.In sys/types.h 40.In sys/ioctl.h 41.In termios.h 42.In libutil.h 43.Ft int 44.Fn openpty "int *amaster" "int *aslave" "char *name" "struct termios *termp" "struct winsize *winp" 45.Ft int 46.Fn forkpty "int *amaster" "char *name" "struct termios *termp" "struct winsize *winp" 47.Sh DESCRIPTION 48The function 49.Fn openpty 50attempts to obtain the next available pseudo-terminal from the system (see 51.Xr pty 4 ) . 52If it successfully finds one, it subsequently tries to change the 53ownership of the slave device to the real UID of the current process, 54the group membership to the group 55.Dq tty 56(if such a group exists in the system), the access permissions for 57reading and writing by the owner, and for writing by the group, and to 58invalidate any current use of the line by calling 59.Xr revoke 2 . 60.Pp 61If the argument 62.Fa name 63is not 64.Dv NULL , 65.Fn openpty 66copies the pathname of the slave pty to this area. The caller is 67responsible for allocating the required space in this array. 68.Pp 69If the arguments 70.Fa termp 71or 72.Fa winp 73are not 74.Dv NULL , 75.Fn openpty 76initializes the termios and window size settings from the structures 77these arguments point to, respectively. 78.Pp 79Upon return, the open file descriptors for the master and slave side 80of the pty are returned in the locations pointed to by 81.Fa amaster 82and 83.Fa aslave , 84respectively. 85.Pp 86.Fn Forkpty 87first calls 88.Fn openpty 89to obtain the next available pseudo-terminal from the system. Upon success, 90it forks off a new process. In the child process, it closes the descriptor 91for the master side of the pty, and calls 92.Xr login_tty 3 93for the slave pty. In the parent process, it closes the descriptor for the 94slave side of the pty. The arguments 95.Fa amaster , 96.Fa name , 97.Fa termp , 98and 99.Fa winp 100have the same meaning as described for 101.Fn openpty . 102.Sh RETURN VALUES 103.Fn Openpty 104returns 0 on success, or -1 on failure. 105.Pp 106.Fn Forkpty 107returns -1 on failure, 0 in the slave process, and the process ID of the 108slave process in the parent process. 109.Sh ERRORS 110On failure, 111.Fn openpty 112will set the global variable 113.Va errno 114to 115.Er ENOENT . 116.Pp 117In addition to this, 118.Fn forkpty 119may set it to any value as described for 120.Xr fork 2 . 121.Sh SEE ALSO 122.Xr chmod 2 , 123.Xr chown 2 , 124.Xr fork 2 , 125.Xr getuid 2 , 126.Xr open 2 , 127.Xr revoke 2 , 128.Xr login_tty 3 , 129.Xr pty 4 , 130.Xr termios 4 , 131.Xr group 5 132.Sh BUGS 133The calling process must have an effective UID of super-user in order 134to perform all the intended actions. No notification will occur if 135.Fn openpty 136or 137.Fn forkpty 138failed to proceed with one of the described steps, as long as they could 139at least allocate the pty at all (and create the new process in the case 140of 141.Fn forkpty ) . 142