dial(3N) dial(3N)
NAME
dial - establish an outgoing terminal line connection
SYNOPSIS
cc [flag ...] file ... -lnsl [library ...]
#include <dial.h>
int dial(CALL call);
void undial(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 alloca-
tion of the terminal device.
The definition of CALL 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; /* unused */
int devlen; /* unused */
} 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- 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 212A 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 pointer to its
device-name should be placed in the line element in the CALL struc-
ture. Legal values for such terminal device names are kept in the
Devices file. In this case, the value of the baud element should be
set to -1. This value will cause dial to determine the correct value
from the Devices file.
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dial(3N) dial(3N)
The telno element is for a pointer to a character string representing
the telephone number to be dialed. Such numbers may consist only of
these characters:
0-9 dial 0-9
* dial *
# dial #
= wait for secondary dial tone
- delay for approximately 4 seconds
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 setting is often
important for certain attributes such as parity and baud-rate.
The CALL elements device and devlen are no longer used. They are
retained in the CALL structure for compatibility reasons.
DIAGNOSTICS
On failure, a negative value indicating the reason for the failure
will be returned. Mnemonics for these negative indices as listed here
are defined in the dial.h header file.
INTRPT -1 /* interrupt occurred */
DHUNG -2 /* dialer hung (no return from write) */
NOANS -3 /* no answer within 10 seconds */
ILLBD -4 /* illegal baud-rate */
APROB -5 /* acu problem (open() failure) */
LPROB -6 /* line problem (open() failure) */
NOLdv -7 /* can't open Devices file */
DVNTA -8 /* requested device not available */
DVNTK -9 /* requested device not known */
NOBDA -10 /* no device available at requested baud */
NOBDK -11 /* no device known at requested baud */
DVNTE -12 /* requested speed does not match */
BADSYS -13 /* system not in Systems file */
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dial(3N) dial(3N)
NOTES
Including the dial.h header file automatically includes the termio.h
header file.
An alarm(2) system call for 3600 seconds is made (and caught) within
the dial module for the purpose of "touching" the LCK.. file and con-
stitutes the device allocation semaphore for the terminal device. Oth-
erwise, uucp(1) 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(2) system call, causing an apparent error return. If
the user program expects to be around for an hour or more, error
returns from reads should be checked for (errno==EINTR), and the read
possibly reissued.
FILES
/etc/uucp/Devices
/etc/uucp/Systems
/var/spool/uucp/LCK..tty-device
SEE ALSO
uucp(1), alarm(2), read(2), write(2), termio(7).
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