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Dd July 27, 2012
Dt OPENPTY 3
Os
Sh NAME
Nm openpty ,
Nm login_tty ,
Nm forkpty
Nd tty utility functions
Sh LIBRARY
Lb libutil
Sh SYNOPSIS
In util.h
Ft int
Fn openpty "int *amaster" "int *aslave" "char *name" "struct termios *termp" "struct winsize *winp"
Ft int
Fn login_tty "int fd"
Ft pid_t
Fn forkpty "int *amaster" "char *name" "struct termios *termp" "struct winsize *winp"
Sh DESCRIPTION
The
Fn openpty ,
Fn login_tty ,
and
Fn forkpty
functions perform manipulations on ttys and pseudo-ttys.
Pp
The
Fn openpty
function finds an available pseudo-tty and returns file descriptors
for the master and slave in
Fa amaster
and
Fa aslave .
If
Fa name
is non-null, the filename of the slave is returned in
Fa name .
The length of
Fa name
is limited to
Dv PATH_MAX
as any other regular path name, so a buffer of this size should be used.
\" .Dv 16
\" characters in the current
\" .Xr ptm 4
\" device driver (including the terminating
\" .Dv NUL )
\" which limits the maximum to
\" .Dv 100,000
\" ptys.
If
Fa termp
is non-null, the terminal parameters of the slave will be set to the
values in
Fa termp .
If
Fa winp
is non-null, the window size of the slave will be set to the values in
Fa winp .
Pp
The
Fn login_tty
function prepares for a login on the tty
Fa fd
(which may be a real tty device, or the slave of a pseudo-tty as
returned by
Fn openpty )
by creating a new session, making
Fa fd
the controlling terminal for the current process, setting
Fa fd
to be the standard input, output, and error streams of the current
process, and closing
Fa fd .
Pp
The
Fn forkpty
function combines
Fn openpty ,
Fn fork ,
and
Fn login_tty
to create a new process operating in a pseudo-tty.
The file descriptor of the master side of the pseudo-tty is returned
(to the parent process only) in
Fa amaster .
The filename of the slave is returned (to both the parent and child
processes) in
Fa name
if
Fa name
is non-null.
The
Fa termp
and
Fa winp
parameters, if non-null, will determine the terminal attributes and
window size of the slave side of the pseudo-tty.
Sh RETURN VALUES
If a call to
Fn openpty ,
Fn login_tty ,
or
Fn forkpty
is not successful, -1 is returned and
Va errno
is set to indicate the error.
Otherwise,
Fn openpty ,
Fn login_tty ,
and the child process of
Fn forkpty
return 0, and the parent process of
Fn forkpty
returns the process ID of the child process.
Sh FILES
Bl -tag -width /dev/[pt]ty[p-zP-T][0-9a-zA-Z] -compact
It Pa /dev/[pt]ty[p-zP-T][0-9a-zA-Z]
El
Sh ERRORS
Fn openpty
will fail if:
Bl -tag -width Er
It Bq Er ENOENT
There are no available ttys.
It Bq Er EPERM
The caller was not the superuser and the
Xr ptm 4
device is missing or not configured.
El
Pp
Fn login_tty
will fail if
Fn ioctl
fails to set
Fa fd
to the controlling terminal of the current process.
Fn forkpty
will fail if either
Fn openpty
or
Fn fork
fails.
Sh SEE ALSO
Xr fork 2

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