dial(3C) dial(3C)
NAME
dial - establish an out-going terminal line connection
SYNOPSIS
#include <dial.h>
int dial (call)
CALL call;
void undial (fd)
int fd;
DESCRIPTION
dial returns a file descriptor for a terminal line open for
read/write. The argument to dial is a CALL structure
(defined in the <dial.h> header file).
When finished with the terminal line, the calling program
must invoke undial to release the semaphore that has been
set during the allocation of the terminal device.
The CALL typedef in the <dial.h> header file is:
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 */
char *device; /* Will hold the name of the device
used to make a connection */
int dev_len /* The length of the device used to
make connection */
} CALL;
The CALL element speed is intended only for use with an
outgoing dialed call, in which case its value should be
either 300 or 1200 to identify the 113A modem, or the high-
speed or low-speed setting on the 212A modem. Note that the
113A modem or the low-speed setting of the 212A modem will
transmit at any rate between 0 and 300 bits per second.
However, the high-speed setting of the 2121 modem transmits
and receives at 1200 bits per second only. The CALL element
baud is for the desired transmission baud rate. For
example, one might set baud to 110 and speed to 300 (or
1200). However, if speed is set to 1200 baud must be set to
high (1200).
If the desired terminal line is a direct line, a string
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dial(3C) dial(3C)
pointer to its device name should be placed in the line
element in the CALL structure. Legal values for such
terminal device names are kept in the L-devices file. In
this case, the value of the baud element need not be
specified as it will be determined from the L-devices file.
The telno element is for a pointer to a character string
representing the telephone number to be dialed. The
termination symbol will be supplied by the dial function,
and should not be included in the telno string passed to
dial in the CALL structure.
The CALL element modem is used to specify modem control for
direct lines. This element should be non-zero if modem
control is required. The CALL element attr is a pointer to
a termio structure, as defined in the <termio.h> header
file. A NULL value for this pointer element may be passed
to the dial function, but if such a structure is included,
the elements specified in it will be set for the outgoing
terminal line before the connection is established. This is
important for attributes such as parity and baud rate.
The CALL element device is used to hold the device name
(cul..) that establishes the connection.
The CALL element devlen is the length of the device name
that is copied into the array device.
FILES
/usr/lib/uucp/L-devices
/usr/spool/uucp/LCK..tty-device
SEE ALSO
uucp(1C), alarm(2), read(2), write(3), termio(7).
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.
INTRPT -1 /* interrupt occurred */
D_HUNG -2 /* dialer hung (no return from write) */
NO_ANS -3 /* no answer within 10 seconds */
ILL_BD -4 /* illegal baud-rate */
A_PROB -5 /* acu problem (open() failure) */
L_PROB -6 /* line problem (open() failure) */
NO_Ldv -7 /* can't open LDEVS file */
DV_NT_A -8 /* requested device not available */
DV_NT_K -9 /* requested device not known */
NO_BD_A -10 /* no device available at requested baud */
NO_BD_K -11 /* no device known at requested baud */
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dial(3C) dial(3C)
WARNINGS
Including the <dial.h> header file automatically includes
the <termio.h> header file.
Because the above routine uses <stdio.h>, the size of
programs not otherwise using standard I/O is increased more
than might be expected.
BUGS
An alarm(2) system call for 3,600 seconds is made (and
caught) within the dial module for the purpose of
``touching'' the LCK.. file and constitutes the device
allocation semaphore for the terminal device. Otherwise,
uucp(1C) may simply delete the LCK.. entry on its 90-minute
clean-up rounds. The alarm may go off while the user
program is in a read(2) or write(3) system call, causing an
apparent error return. If the user program is to run for an
hour or more, error returns from reads should be checked for
(errno==EINTR), and the read possibly reissued.
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