getttyen.3

操作系统设计与实现源码

.TH GETTTYENT 3
.SH NAME
getttyent, getttynam, setttyent, endttyent \- interface to /etc/ttytab
.SH SYNOPSIS
.ft B
.nf
#include <ttyent.h>

struct ttyent *getttyent(void)
struct ttyent *getttynam(const char *\fIname\fP)
int setttyent(void)
void endttyent(void)
.fi
.ft P
.SH DESCRIPTION
The
.B getttyent
functions provide an interface to the /etc/ttytab.  (See
.BR ttytab (5)).
.PP
To read one of these files one calls
.B getttyent()
several times to read the entries in the table until NULL is returned for
end-of-file.
.PP
.B Getttyname()
searches the
.B ttytab
file for the given terminal device.  It is equivalent to a call to
.BR setttyent(),
several calls to
.B getttyent()
to locate the entry, and a final
.B endttyent()
to close the file.
.PP
.B Setttyent()
opens or rewinds the ttytab database, and
.B endttyent() closes it.
.B Getttyent()
opens the database if not already open, but does not close it.
.PP
The struct ttyent is defined by <ttyent.h> as follows:
.sp
.nf
.ta +4n +6n +15n
struct ttyent {
	char	*ty_name;	/* Name of the terminal device. */
	char	*ty_type;	/* Terminal type name (termcap(3)). */
	char	**ty_getty;	/* Program to run, normally getty. */
	char	**ty_init;	/* Initialization command, normally stty. */
};
.fi
.PP
A valid entry has at least two strings, so both
.B ty_name
and
.B ty_type
are filled in.  The optional
.B ty_getty
and
.B ty_init
may be NULL (field omitted), point to a pointer that is NULL (null lenght
field, i.e. ""), or an array of strings terminated by a NULL (field
present).  For now no useful distinction can be made between a omitted field
and an empty field, so treat both cases as an omission.
.SH FILES
.TP 15
.B /etc/ttytab
The terminal device database
.SH "SEE ALSO"
.BR ttyname (3),
.BR ttyslot (3),
.BR ttytab (5),
.BR init (8).
.SH DIAGNOSTICS
.B Setttyent()
has the same return value and error codes as the
.BR open (2)
call it uses to open the ttytab file.  The
.BI get xxx ()
functions return NULL on end of file, entry not found, or error.  You can
set
.B errno
to zero before the call and check it after.
.SH NOTES
.B Getttyent()
and
.B getttynam()
return a pointer to static storage that is overwritten in each call.
.PP
The Minix
.B struct ttyent
has only the
.B ty_name
and
.B ty_type
fields in common with the BSD implementation.  This does not seem to be a
problem, because most third party software that need to know about terminals
only look at the
.B ty_name
field.
.SH AUTHOR
Kees J. Bot ([e-mail])