pearmana@prlhp1.prl.philips.co.uk (Andy Pearman) (02/01/90)
Could someone please remind me how the relation between
/dev/tty and /dev/tty01 etc works
i.e. If I do:
echo "Hello" > /dev/tty
it comes out on /dev/tty01 etc
On doing an ls I see no obvious links and besides
everyones /dev/tty points somewhere different.
If you could shed some light on this matter I would be very
grateful.
Andy
--
Andy Pearman, Computer Dept, Philips Research Labs, Redhill, Surrey, England.
pearmana@prl.philips.co.ukjik@athena.mit.edu (Jonathan I. Kamens) (02/06/90)
In article <1044@prlhp1.prl.philips.co.uk>, pearmana@prlhp1.prl.philips.co.uk (Andy Pearman) writes: > Could someone please remind me how the relation between > > /dev/tty and /dev/tty01 etc works RTFM, that'll at least get you started. At least in BSD, the following paragraph appears in the man page tty(4): The file /dev/tty is, in each process, a synonym for a con- trol terminal associated with that process. It is useful for programs that wish to be sure of writing messages on the terminal no matter how output has been redirected. It can also be used for programs that demand a file name for out- put, when typed output is desired and it is tiresome to find out which terminal is currently in use. The actual link between "/dev/tty" and whatever tty you happen to be using is accomplished in the kernel -- when a process attempts to open /dev/tty, the file descriptor returned by the kernel is a file descriptor for the controlling terminal of the process. The name "/dev/tty" is not really what's significant; instead, the major and minor device numbers of the file /dev/tty are what tell the kernel that it should be treated as the tty file. If you were to create another device with the same device numbers and a different name, the kernel would still give you an fd for the controlling terminal if you were to open it. Jonathan Kamens USnail: MIT Project Athena 11 Ashford Terrace jik@Athena.MIT.EDU Allston, MA 02134 Office: 617-253-8495 Home: 617-782-0710
donlash@uncle.UUCP (Donald Lashomb) (02/10/90)
In simple terms: /dev/tty is not connected to any single *real* tty, it is a special program that connects to ->your<- terminal, whatever it may be. Things like /dev/tty01..02..n are connected to *real* ttys. -Don
jik@athena.mit.edu (Jonathan I. Kamens) (02/11/90)
In article <689@uncle.UUCP>, donlash@uncle.UUCP (Donald Lashomb) writes: > In simple terms: /dev/tty is not connected to any single *real* tty, it > is a special program that connects to ->your<- terminal, whatever it may be. > Things like /dev/tty01..02..n are connected to *real* ttys. Two points: 1. /dev/tty is not a "special program", it is a "special device". A minor but significant difference. 2. Not all numbered tty's are connected to "*real* ttys"; I'm not even sure what you mean by a "real" tty, so I'm assuming that by "real" you mean "physical". However, pseudo-ttys (ptys) don't fall into that category, and yet a program running on a pty which opens /dev/tty *will* get something useful. Jonathan Kamens USnail: MIT Project Athena 11 Ashford Terrace jik@Athena.MIT.EDU Allston, MA 02134 Office: 617-253-8495 Home: 617-782-0710