UNIX for Dummies Questions & Answers

On my mgetty man page I see:

Code:

       -m 'expect send ...'
              Set the "chat sequence" that is used to initialize the modem. For an empty expect part, use empty double
              quotes  ("").  Since  the  sequence contains spaces, you have to enclose all of it in single quotes('').
              Example:

              mgetty -m '"" ATH0 OK'

Don't you also have "-m"? I have never used mgetty and I probably never will. I don't have a modem either. But for years I used modems on Unix with getty and its file gettydefs so this seems very familiar. mgettydefs is used to configure the port. getty was (and I assume the mgetty is) intended to set things up so the system is ready to accept an incoming call.

We did not have a great way to send AT command sto the modem on the fly. Instead we would program the modem via AT commands and the modem would simply remember it's configuration somehow. Once in a blue moon we might need to reprogram a modem, but in general this never occurred.

I have not seen a modem for a long time. I would hope that modern modems (if they exist) can remember their configuration. If your modem is dropping its config on a regular basis, maybe it need a new battery for its memory or something like that.

As I type this in, more memories are returning. I wonder if that is a good thing... We had a few modems that would "swing both ways". That is we used them both for outgoing and incoming calls. The getty would program the port (say, /dev/tty01) via gettydefs to use modem control. The getty program would issue an open() system call which would block waiting for a signal from the modem (DCD, data carrier detect or DSR, data set ready, not sure which). This signal would not arrive until the modem answered an incoming call. Meanwhile we could use programs like uucico or cu to place outgoing calls. They would open the port with no modem control and thus the open would succeed immediately. They had ways to send AT commands and this was always needed since we had to do ATDT7035551212 or something like that to tell the modem which phone number to call. Because cu or uucico had opened the port, that getty open was now blocked because another process has the port. When the modem control signal arrived the getty open stayed blocked. When cu or uucico was finished, it would put the modem back in the state in which it found it and close the port. Now it was ready to answer an incoming call again and that waiting open(0 call issued long ago by getty was still valid.

I don't know how much of this is useful to you. If you still need help, reveal a few clues so someone can help you. What version of what OS? What system? What modem?