dial.3c

<B>Digital的Unix操作系统VAX 4.2源码</B>

.\"	@(#)dial.3c	5.2 of 5/18/82
.TH dial 3c VAX "" Unsupported
.SH Name
dial \- establish an out-going terminal line connection
.SH Syntax
.B #include <dial.h>
.PP
int dial(\fIcall\fP)
.br
\s-1CALL\s+1 \(**\fIcall\fP;
.PP
void undial(\fIfd\fP)
.br
int \fIfd\fP;
.SH Description
The 
.PN dial 
routine
returns a file-descriptor for a terminal line open for read/write.
The argument to
.PN dial 
is a \s-1CALL\s+1 structure which is defined in the
<dial.h> header file.
.PP
When finished with the terminal line,
the calling program must invoke
.PN undial
to release the semaphore that has been set
during the allocation of the terminal device.
.PP
The \s-1CALL\s+1 typedef in the 
<dial.h> header file is:
.EX
typedef struct {
	struct termio \(**attr;	/\(** pointer to termio attribute struct \(**/
	int	baud;	/\(** transmission data rate \(**/
	int	speed;	/\(** 212A modem: low=300, high=1200 \(**/
	char	\(**line;	/\(** device name for out-going line \(**/
	char	\(**telno;	/\(** pointer to tel-no digits string \(**/
	int	modem;	/\(** specify modem control for direct lines \(**/
} \s-1CALL\s+1;
.EE
The \s-1CALL\s+1 element
.PN speed
is intended only for use with
an outgoing dialed call.
.PP
The \s-1CALL\s+1 element
.PN baud
is for the desired transmission
baud rate.
For example, one might set
baud to 110 and speed
to 300 (or 1200).
.PP
If the desired terminal line is a direct line, a string
pointer to its device-name should be placed in the
.PN line 
element in the \s-1CALL\s+1 structure.
Legal values for such terminal device names are kept in the
L-devices file.
In this case, the value of the
.PN baud
element need not be specified as it is determined
from the
L-devices
file.
.PP
The
.PN telno\^
element is for a pointer to a character string
representing the telephone number to be dialed.
The termination symbol
is supplied by the
.PN dial
function, and should not be included in the
.PN telno
string passed to
.PN dial
in the \s-1CALL\s+1 structure.
.PP
The \s-1CALL\s+1 element
.PN modem
is used to specify modem control for direct lines.
This element should be non-zero if modem control is required.
.PP
The \s-1CALL\s+1 element
.PN attr
is a pointer to a
.PN termio
structure, as defined in the
termio.h header file.
A \s-1NULL\s+1 value for this pointer element may be passed to
the
.PN dial
function, but if such a structure is included, the elements specified
in it are set for the outgoing terminal line before the connection
is established.
This is often important for certain attributes
such as parity and baud-rate.
.SH Restrictions
Including the
.B <dial.h>
header file automatically includes the
.B <termio.h> header file.
.PP
An
.MS alarm 3
system call for 3600 seconds is made (and caught) within the
.PN dial
module for the purpose of ``touching'' the \fI\s-1LCK\s+1..\fP file
and constitutes the device allocation semaphore for the terminal
device.
Otherwise,
.MS uucp 1c
may simply delete the \fI\s-1LCK\s+1..\fP entry on its 90-minute clean-up rounds.
The alarm may go off while the user program is in a
.MS read 2
or
.MS write 2
system call, causing an apparent error return.
If the user program expects to be around for an hour or more, error
returns from
.IR read s
should be checked for \fB(errno==\s-1EINTR\s+1)\fP, and the
.I read\^
possibly reissued.
.SH Diagnostics
On failure, a negative value indicating the reason for
the failure is returned.
Mnemonics for these negative indices as listed here are defined
in the <dial.h>
header file.
.sp 2
.nf
.ta .5i 1.3i 2.0i
	\s-1INTRPT\s+1	\-1	/\(** interrupt occured \(**/
	\s-1D_HUNG\s+1	\-2	/\(** dialer hung (no return from write) \(**/
	\s-1NO_ANS\s+1	\-3	/\(** no answer within 10 seconds \(**/
	\s-1ILL_BD\s+1	\-4	/\(** illegal baud-rate \(**/
	\s-1A_PROB\s+1	\-5	/\(** acu problem (open() failure) \(**/
	\s-1L_PROB\s+1	\-6	/\(** line problem (open() failure) \(**/
	\s-1NO_L\s+1dv	\-7	/\(** can't open \s-1LDEVS\s+1 file \(**/
	\s-1DV_NT_A\s+1	\-8	/\(** requested device not available \(**/
	\s-1DV_NT_E\s+1	\-12	/\(** requested speed does not match \(**/
	\s-1DV_NT_K\s+1	\-9	/\(** requested device not known \(**/
	\s-1NO_BD_A\s+1	\-10	/\(** no device available at requested baud \(**/
	\s-1NO_BD_K\s+1	\-11	/\(** no device known at requested baud \(**/
.fi
.SH Files
\f(CW/usr/lib/uucp/L-devices\fP
.br
\f(CW/usr/spool/uucp/\s-1LCK\s+1..\fItty-device\fP
.SH See Also
uucp(1c), alarm(3), read(2), write(2), termio(7)