Finally document the interfaces found in libutil. While being here,

also add the missing declaration of forkpty() to libutil.h.

Btw., the calling interface for login(3) is crude.  Some better
abstraction is needed, perhaps similar to logwtmp(3).

2.2 candidate, but i'll wait for the spelling police first. :)

1 files changed, 143 insertions, 0 deletions

diff --git a/lib/libutil/pty.3 b/lib/libutil/pty.3
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+.\" 
+.\" Copyright (c) 1996 Joerg Wunsch
+.\" 
+.\" All rights reserved.
+.\" 
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
+.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
+.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+.\" 
+.\" $Id$
+.\" "
+.Dd December 29, 1996
+.Os
+.Dt PTY 3
+.Sh NAME
+.Nm openpty, forkpty
+.Nd auxiliary functions to obtain a pseudo-terminal
+.Sh SYNOPSIS
+.Fd #include <sys/types.h>
+.Fd #include <sys/ioctl.h>
+.Fd #include <termios.h>
+.Fd #include <libutil.h>
+.Ft int
+.Fn openpty "int *amaster" "int *aslave" "char *name" "struct termios *termp" "struct winsize *winp"
+.Ft int
+.Fn forkpty "int *amaster" "char *name" "struct termios *termp" "struct winsize *winp"
+.Pp
+Link with
+.Va -lutil
+on the
+.Xr cc 1
+command line.
+.Sh DESCRIPTION
+The function
+.Nm openpty
+attempts to obtain the next available pseudo-terminal from the system (see
+.Xr pty 4 ) .
+If it successfully found one, it subsequently tries to change the
+ownership of the slave device to the real UID of the current process,
+the group membership to the group
+.Dq tty
+(if such a group exists in the system), the access permissions for
+reading and writing by the owner, and for writing by the group, and to
+invalidate any current use of the line by calling
+.Xr revoke 2 .
+.Pp
+If the argument
+.Ar name
+is not
+.Dv NULL ,
+.Nm openpty
+copies the pathname of the slave pty to this area.  The caller is
+responsible to allocate the required space in this array.
+.Pp
+If the arguments
+.Ar termp
+or
+.Ar winp
+are not
+.Dv NULL ,
+.Nm openpty
+initializes the termios and window size settings from the structures
+these argument point to, respectively.
+.Pp
+Upon return, the open filedescriptors for the master and slave side
+of the pty are returned in the locations pointed to by
+.Ar amaster
+and
+.Ar aslave ,
+respectively.
+.Pp
+.Nm Forkpty
+first calls
+.Xr openpty 3
+to obtain the next available pseudo-terminal from the system.  Upon success,
+it forks off a new process.  In the child process, it closes the descriptor
+for the master side of the pty, and calls
+.Xr login_tty 3
+for the slave pty.  In the parent process, it closes the descriptor for the
+slave side of the pty.  The arguments
+.Ar amaster ,
+.Ar name ,
+.Ar termp ,
+and
+.Ar winp
+have the same meaning as described for
+.Nm openpty .
+.Sh RETURN VALUES
+.Nm Openpty
+returns 0 on success, or -1 on failure.
+.Pp
+.Nm Forkpty
+returns -1 on failure, 0 in the slave process, and the process ID of the
+slave process in the parent process.
+.Sh ERRORS
+On failure,
+.Nm openpty
+will set the global variable
+.Dv errno
+to
+.Er ENOENT .
+.Pp
+In addition to this,
+.Nm forkpty
+may set it to any value as described for
+.Xr fork 2 .
+.Sh SEE ALSO
+.Xr chmod 2 ,
+.Xr chown 2 ,
+.Xr fork 2 ,
+.Xr getuid 2 ,
+.Xr open 2 ,
+.Xr revoke 2 ,
+.Xr login_tty 3 ,
+.Xr termios 3 ,
+.Xr pty 4 ,
+.Xr group 5
+.Sh BUGS
+The calling process must have an effective UID of super-user in order
+to perform all the intended actions.  No notification will occur if
+.Nm openpty
+or
+.Nm forkpty
+failed to proceed with one of the described steps, as long as they could
+at least allocate the pty at all (and create the new process in the case
+of
+.Nm forkpty ) .