libc/gen/getttyent.3

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.\"     @(#)getttyent.3	8.1 (Berkeley) 6/4/93
.\" $FreeBSD: src/lib/libc/gen/getttyent.3,v 1.15 2007/01/09 00:27:54 imp Exp $
.\"
.Dd September 20, 2023
.Dt GETTTYENT 3
.Os
.Sh NAME
.Nm getttyent ,
.Nm getttynam ,
.Nm setttyent ,
.Nm endttyent ,
.Nm isdialuptty ,
.Nm isnettty
.Nd
.Xr ttys 5
file routines
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In ttyent.h
.Ft struct ttyent *
.Fn getttyent void
.Ft struct ttyent *
.Fn getttynam "const char *name"
.Ft int
.Fn setttyent void
.Ft int
.Fn endttyent void
.Ft int
.Fn isdialuptty "const char *name"
.Ft int
.Fn isnettty "const char *name"
.Sh DESCRIPTION
The
.Fn getttyent ,
and
.Fn getttynam
functions
each return a pointer to an object, with the following structure,
containing the broken-out fields of a line from the tty description
file.
.Bd -literal
struct ttyent {
	char	*ty_name;	/* terminal device name */
	char	*ty_getty;	/* command to execute, usually getty */
	char	*ty_type;	/* terminal type for termcap */
	int	ty_status;	/* status flags */
	char	*ty_window;	/* command to start up window manager */
	char	*ty_comment;	/* comment field */
	char	*ty_group;	/* tty group name */
};
.Ed
.Pp
The fields are as follows:
.Bl -tag -width ".Fa ty_comment"
.It Fa ty_name
The name of the character-special file.
.It Fa ty_getty
The name of the command invoked by
.Xr init 8
to initialize tty line characteristics.
.It Fa ty_type
The name of the default terminal type connected to this tty line.
.It Fa ty_status
A mask of bit fields which indicate various actions allowed on this
tty line.
The possible flags are as follows:
.Bl -tag -width ".Dv TTY_IFCONSOLE"
.It Dv TTY_ON
Enables logins (i.e.,
.Xr init 8
will start the command referenced by
.Fa ty_getty
on this entry).
.It Dv TTY_SECURE
Allow users with a uid of 0 to login on this terminal.
.It Dv TTY_DIALUP
Identifies a tty as a dialin line.
If this flag is set, then
.Fn isdialuptty
will return a non-zero value.
.It Dv TTY_NETWORK
Identifies a tty used for network connections.
If this flag is set, then
.Fn isnettty
will return a non-zero value.
.It TTY_IFCONSOLE
Only enables a tty if it's the console.
.It TTY_IFEXISTS
Only enables a tty if it exists.
.El
.It Fa ty_window
The command to execute for a window system associated with the line.
.It Fa ty_group
A group name to which the tty belongs.
If no group is specified in the ttys description file,
then the tty is placed in an anonymous group called
.Dq none .
.It Fa ty_comment
Any trailing comment field, with any leading hash marks
.Pq #
or whitespace removed.
.El
.Pp
If any of the fields pointing to character strings are unspecified,
they are returned as null pointers.
The field
.Fa ty_status
will be zero if no flag values are specified.
.Pp
See
.Xr ttys 5
for a more complete discussion of the meaning and usage of the
fields.
.Pp
The
.Fn getttyent
function
reads the next line from the ttys file, opening the file if necessary.
The
.Fn setttyent
function
rewinds the file if open, or opens the file if it is unopened.
The
.Fn endttyent
function
closes any open files.
.Pp
The
.Fn getttynam
function
searches from the beginning of the file until a matching
.Fa name
is found
(or until
.Dv EOF
is encountered).
.Sh RETURN VALUES
The routines
.Fn getttyent
and
.Fn getttynam
return a null pointer on
.Dv EOF
or error.
The
.Fn setttyent
function
and
.Fn endttyent
return 0 on failure and 1 on success.
.Pp
The routines
.Fn isdialuptty
and
.Fn isnettty
return non-zero if the dialup or network flag is set for the
tty entry relating to the tty named by the argument, and
zero otherwise.
.Sh FILES
.Bl -tag -width ".Pa /etc/ttys" -compact
.It Pa /etc/ttys
.El
.Sh SEE ALSO
.Xr login 1 ,
.Xr gettytab 5 ,
.Xr termcap 5 ,
.Xr ttys 5 ,
.Xr getty 8 ,
.Xr init 8
.Sh HISTORY
The
.Fn getttyent ,
.Fn getttynam ,
.Fn setttyent ,
and
.Fn endttyent
functions appeared in
.Bx 4.3 .
.Sh BUGS
These functions use static data storage;
if the data is needed for future use, it should be
copied before any subsequent calls overwrite it.