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: head/lib/libutil/pty.3 206622 2010-04-14 19:08:06Z uqs $ 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 changes 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 57invalidates 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. 66The 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 86The 87.Fn forkpty 88function first calls 89.Fn openpty 90to obtain the next available pseudo-terminal from the system. 91Upon success, 92it forks off a new process. 93In the child process, it closes the descriptor 94for the master side of the pty, and calls 95.Xr login_tty 3 96for the slave pty. 97In the parent process, it closes the descriptor for the 98slave side of the pty. 99The arguments 100.Fa amaster , 101.Fa name , 102.Fa termp , 103and 104.Fa winp 105have the same meaning as described for 106.Fn openpty . 107.Sh RETURN VALUES 108The 109.Fn openpty 110function returns 0 on success, or -1 on failure. 111.Pp 112The 113.Fn forkpty 114function returns -1 on failure, 0 in the slave process, and the process ID of 115the slave process in the parent process. 116.Sh ERRORS 117The 118.Fn openpty 119function may fail and set the global variable 120.Dv errno 121for any of the errors specified for the 122.Xr grantpt 3 , 123.Xr posix_openpt 3 , 124.Xr ptsname 3 , 125and 126.Xr unlockpt 3 127functions and the 128.Xr revoke 2 129system call. 130.Pp 131In addition to this, 132.Fn forkpty 133may set it to any value as described for 134.Xr fork 2 . 135.Sh SEE ALSO 136.Xr chmod 2 , 137.Xr chown 2 , 138.Xr fork 2 , 139.Xr getuid 2 , 140.Xr open 2 , 141.Xr revoke 2 , 142.Xr login_tty 3 , 143.Xr pty 4 , 144.Xr termios 4 , 145.Xr group 5 146