On Sat, Jun 26, 2021 at 08:42:26AM -0400, Cindy Sue Causey wrote: > On 6/26/21, Andrei POPESCU <andreimpopescu@gmail.com> wrote: [...] > > Well, it makes perfect sense if you remember that "everything is a > > file", even if there are exceptions (e.g. network devices). > > > Hopefully I'm reading this right. While on dialup, I spent A LOT of > time battling a well-known closed source modem tty* driver. Out of > desperation, I could sometimes get it to work by copying it between > hard drives that contained separate operating systems. > > BUT you can't just e.g. "cp" or "right click > copy" it over. It would > fail with a "Can't copy special file" error message. I know this > because I just did it again with ttyS0. You CAN rsync it between > partitions, and it would be viable, usable. Wait a sec. You are not trying to copy /dev/ttyS0 (or its kin)? Because that won't really make much sense. Or, well, it will perhaps do surprising things. See, /dev/ttyS0 is a representation of an external device (your first serial interface, if your computer still has such a thing). You can open it, read from it (which will yield incoming characters), write to it (which will send the characters out, if all goes well) -- so to your applications it presents an interface similar to the one a file presents. This is Andrei's quote "everything is a file". If you now copy /dev/ttyS0 to /tmp, e.g. sudo cp /dev/ttyS0 /tmp and assuming there's something connected to it and sending us characters, there will be an ever-growing /tmp/ttyS0 and the copy will terminate the moment the serial connection's other side "hangs up". Now if you do sudo cp -a /dev/ttyS0 /tmp you get something completely different: a device file (referring to the exact same device as your original). Don't forget to remove them after: your system administrator might get mighty confused finding a device file in /tmp :-) Cheers - t
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