getttyent.3

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 3 代码 · 共 154 行

.\" SCCSID: @(#)getttyent.3	3.1	11/24/87
.TH getttyent 3
.SH Name
getttyent, getttynam, setttyent, endttyent \- get ttys file entry 
.SH Syntax
#include <ttyent.h>
.br
struct ttyent *getttyent()
.br
struct ttyent *getttynam(\fIname\fR) char *\fIname;\fR
.br
void setttyent()
.br
void endttyent() 
.SH Arguments
.TP
\fIname\fP
The name of the terminal's special file in the 
.PN /dev
directory.
.SH Description
.NXR "getttyent subroutine"
.NXR "getttynam subroutine"
.NXR "settyent subroutine"
.NXR "endttyent subroutine"
.NXR "ttys file" "accessing data"
These functions allow a program to access data in the
file 
.PN /etc/ttys .
The
.PN getttyent
function reads the 
.PN /etc/ttys
file line by line, opening the file if
necessary.
.PN setttyent 
rewinds the file, and
.PN endttyent
closes it.
.PN getttynam
searches from the beginning of the file until a matching name
is found, or until end-of-file is encountered.
.PP
The functions 
.PN getttyent
and 
.PN getttynam
each return a pointer to an object
that has the following structure. 
Each element of the structure contains
one field of a line in the 
.PN /etc/ttys
file.
.EX 0
struct ttyent {         /* see getttyent(3) */
       char *ty_name;   /* terminal device name */
       char *ty_getty;  /* command to execute, usually getty */
       char *ty_type;   /* terminal type for termcap (3x) */
       int  ty_status;  /* status flags (see below for defines) */
       char *ty_window; /* command to start up window manager */
       char *ty_comment;/* usually the location of the terminal */
       };

#define TTY_ON      0x1  /* enable logins (startup getty) */
#define TTY_SECURE  0x2  /* allow root to login */
#define TTY_LOCAL   0x4  /* line is local direct connect and
                         should ignore modem signals */
#define TTY_SHARED  0x8  /* line is shared:  it can be use
                         for both incoming and outgoing
                         connections. */
#define TTY_TRACK   0x10 /* track modem status changes */
#define TTY_TERMIO  0x20 /* open line with termio defaults */
#define TTY_SU      0x40 /* disallow su to root */   

extern struct ttyent *getttyent();
extern struct ttyent *getttynam();
.EE
A description of the fields follows:
.NXR "ttys file" "field definitions"
.IP ty_name
is the name of the terminal's special file in
the directory 
.PN /dev .
.IP ty_getty
is the command 
invoked by 
.PN init
to initialize terminal line characteristics.
This command is usually
.MS getty 8 ,
but any arbitrary command  can
be  used.  A typical use is to initiate a terminal
emulator in a window system.
.IP ty_type
is the name of the default terminal type  connected
to this tty line.  This is typically a
name from the 
.MS termcap 5 
data base.  The
environment variable `TERM' is initialized with
this name by 
.MS login 1 .
.IP ty_status
is a mask of bit flags that indicate  various
actions allowed on this terminal line. The
following is a description of each flag.
.RS
.IP TTY_ON
Enables logins.  For instance, 
.MS init 8
will start the specified 
.PN getty
command on this entry.
.IP TTY_SECURE 
Allows root to login on this  terminal.  TTY_ON must
also be
included for this to work.
.IP TTY_LOCAL
Indicates that the line is to ignore modem signals.  
.IP TTY_SHARED
Indicates that the line can be used for both incoming
and outgoing connections.
.IP TTY_TERMIO
Indicates that a line is to be opened with default
terminal attributes which are compliant with System
Five termio defaults.  The line discipline will be set
to be TERMIODISC.
.IP TTY_SU
Indicates that a user is allowed to su to root on this terminal.
The default if this flag is not set is that a user cannot su to root
on this terminal.
.RE
.IP ty_window
is the quoted string of a command to execute
for a window system associated with the line.
If no command is specified, this field is a null
string.
.IP ty_comment
Currently unused. 
.SH Restrictions
.NXR "getttyent subroutine" "restrictions"
.PP
The information returned is in a static area, so
you must copy it to save it.  
.SH Return Values
.PP
A null pointer (0) is returned on an end-of-file
or error.
.SH Files
.PN /etc/ttys 
The file examined by these routines. 
.SH See Also
ttyname(3), ttys(5), init(8)