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.\" 28.Dd December 29, 1996 29.Dt PTY 3 30.Os 31.Sh NAME 32.Nm openpty , 33.Nm forkpty 34.Nd auxiliary functions to obtain a pseudo-terminal 35.Sh LIBRARY 36.Lb libutil 37.Sh SYNOPSIS 38.In sys/types.h 39.In sys/ioctl.h 40.In termios.h 41.In libutil.h 42.Ft int 43.Fn openpty "int *amaster" "int *aslave" "char *name" "struct termios *termp" "struct winsize *winp" 44.Ft int 45.Fn forkpty "int *amaster" "char *name" "struct termios *termp" "struct winsize *winp" 46.Sh DESCRIPTION 47The function 48.Fn openpty 49attempts to obtain the next available pseudo-terminal from the system (see 50.Xr pty 4 ) . 51If it successfully finds one, it subsequently tries to change the 52ownership of the slave device to the real UID of the current process, 53the group membership to the group 54.Dq tty 55(if such a group exists in the system), the access permissions for 56reading and writing by the owner, and for writing by the group, and to 57invalidate any current use of the line by calling 58.Xr revoke 2 . 59.Pp 60If the argument 61.Fa name 62is not 63.Dv NULL , 64.Fn openpty 65copies the pathname of the slave pty to this area. The caller is 66responsible for allocating the required space in this array. 67.Pp 68If the arguments 69.Fa termp 70or 71.Fa winp 72are not 73.Dv NULL , 74.Fn openpty 75initializes the termios and window size settings from the structures 76these arguments point to, respectively. 77.Pp 78Upon return, the open file descriptors for the master and slave side 79of the pty are returned in the locations pointed to by 80.Fa amaster 81and 82.Fa aslave , 83respectively. 84.Pp 85.Fn Forkpty 86first calls 87.Fn openpty 88to obtain the next available pseudo-terminal from the system. Upon success, 89it forks off a new process. In the child process, it closes the descriptor 90for the master side of the pty, and calls 91.Xr login_tty 3 92for the slave pty. In the parent process, it closes the descriptor for the 93slave side of the pty. The arguments 94.Fa amaster , 95.Fa name , 96.Fa termp , 97and 98.Fa winp 99have the same meaning as described for 100.Fn openpty . 101.Sh RETURN VALUES 102.Fn Openpty 103returns 0 on success, or -1 on failure. 104.Pp 105.Fn Forkpty 106returns -1 on failure, 0 in the slave process, and the process ID of the 107slave process in the parent process. 108.Sh ERRORS 109On failure, 110.Fn openpty 111will set the global variable 112.Va errno 113to 114.Er ENOENT . 115.Pp 116In addition to this, 117.Fn forkpty 118may set it to any value as described for 119.Xr fork 2 . 120.Sh SEE ALSO 121.Xr chmod 2 , 122.Xr chown 2 , 123.Xr fork 2 , 124.Xr getuid 2 , 125.Xr open 2 , 126.Xr revoke 2 , 127.Xr login_tty 3 , 128.Xr pty 4 , 129.Xr termios 4 , 130.Xr group 5 131.Sh BUGS 132The calling process must have an effective UID of super-user in order 133to perform all the intended actions. No notification will occur if 134.Fn openpty 135or 136.Fn forkpty 137failed to proceed with one of the described steps, as long as they could 138at least allocate the pty at all (and create the new process in the case 139of 140.Fn forkpty ) . 141