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.\" $Id$ 27.\" " 28.Dd December 29, 1996 29.Os 30.Dt PTY 3 31.Sh NAME 32.Nm openpty, forkpty 33.Nd auxiliary functions to obtain a pseudo-terminal 34.Sh SYNOPSIS 35.Fd #include <sys/types.h> 36.Fd #include <sys/ioctl.h> 37.Fd #include <termios.h> 38.Fd #include <libutil.h> 39.Ft int 40.Fn openpty "int *amaster" "int *aslave" "char *name" "struct termios *termp" "struct winsize *winp" 41.Ft int 42.Fn forkpty "int *amaster" "char *name" "struct termios *termp" "struct winsize *winp" 43.Pp 44Link with 45.Va -lutil 46on the 47.Xr cc 1 48command line. 49.Sh DESCRIPTION 50The function 51.Nm openpty 52attempts to obtain the next available pseudo-terminal from the system (see 53.Xr pty 4 ) . 54If it successfully found one, it subsequently tries to change the 55ownership of the slave device to the real UID of the current process, 56the group membership to the group 57.Dq tty 58(if such a group exists in the system), the access permissions for 59reading and writing by the owner, and for writing by the group, and to 60invalidate any current use of the line by calling 61.Xr revoke 2 . 62.Pp 63If the argument 64.Ar name 65is not 66.Dv NULL , 67.Nm openpty 68copies the pathname of the slave pty to this area. The caller is 69responsible to allocate the required space in this array. 70.Pp 71If the arguments 72.Ar termp 73or 74.Ar winp 75are not 76.Dv NULL , 77.Nm openpty 78initializes the termios and window size settings from the structures 79these argument point to, respectively. 80.Pp 81Upon return, the open filedescriptors for the master and slave side 82of the pty are returned in the locations pointed to by 83.Ar amaster 84and 85.Ar aslave , 86respectively. 87.Pp 88.Nm Forkpty 89first calls 90.Xr openpty 3 91to obtain the next available pseudo-terminal from the system. Upon success, 92it forks off a new process. In the child process, it closes the descriptor 93for the master side of the pty, and calls 94.Xr login_tty 3 95for the slave pty. In the parent process, it closes the descriptor for the 96slave side of the pty. The arguments 97.Ar amaster , 98.Ar name , 99.Ar termp , 100and 101.Ar winp 102have the same meaning as described for 103.Nm openpty . 104.Sh RETURN VALUES 105.Nm Openpty 106returns 0 on success, or -1 on failure. 107.Pp 108.Nm Forkpty 109returns -1 on failure, 0 in the slave process, and the process ID of the 110slave process in the parent process. 111.Sh ERRORS 112On failure, 113.Nm openpty 114will set the global variable 115.Dv errno 116to 117.Er ENOENT . 118.Pp 119In addition to this, 120.Nm forkpty 121may set it to any value as described for 122.Xr fork 2 . 123.Sh SEE ALSO 124.Xr chmod 2 , 125.Xr chown 2 , 126.Xr fork 2 , 127.Xr getuid 2 , 128.Xr open 2 , 129.Xr revoke 2 , 130.Xr login_tty 3 , 131.Xr termios 3 , 132.Xr pty 4 , 133.Xr group 5 134.Sh BUGS 135The calling process must have an effective UID of super-user in order 136to perform all the intended actions. No notification will occur if 137.Nm openpty 138or 139.Nm forkpty 140failed to proceed with one of the described steps, as long as they could 141at least allocate the pty at all (and create the new process in the case 142of 143.Nm forkpty ) . 144