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 (de- fined 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 out- going 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 exam- ple, one might set baud to 110 and speed to 300 (or 1200). April, 1990 1
dial(3C) dial(3C)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 ele- ment 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 termi- nation 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 nonzero if modem con- trol 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 ele- ments specified in it will be set for the outgoing terminal line before the connection is established. This is impor- tant 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 dev_len is the length of the device name that is copied into the array device. ERRORS 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 */ 2 April, 1990
dial(3C) dial(3C)FILES /usr/lib/uucp/L-devices /usr/spool/uucp/LCK..tty-device SEE ALSO uucp(1C), alarm(2), read(2), write(2), termio(7). WARNINGS Including the <dial.h> header file automatically includes the <termio.h> header file. Because the above routine uses <stdio.h>, the size of pro- grams 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 ``touch- ing'' 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(2) 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. April, 1990 3