tty / pty

[j773303]

Could someone explain what's the mean of tty
and pty, and what's the difference between both? Thanks.

[Michael Tully]

The basic meaning is:

tty=a fixed terminal e.g. a modem, a terminal directly cabled to a MUX board or serial port.

pty= pseudo terminal. Any telnet session will have a pty assigned as opposed to a directly connect terminal or modem. The operating system will allocate the next available pty terminal identity.

There are kernel parameters that allow/control the number of these. These are 'npty' 'nstrtel' and 'nstrpty'

[j773303]

I'm still confused. Why command tty and pty
only show /dev/ttyr0. How about /dev/ptyr0?

[Yogeeraj_1 · Accepted solution]

hi,

FYI:
tty was developed by AT&T.
pty was developed by HP

see below:
==============================
K250: dev>ll *tyr5
crw-rw-rw- 2 root root 16 0x000025 Jun 10 1996 ptyr5
crw--w--w- 2 pbh tty 17 0x000025 Dec 9 10:19 ttyr5
K250: dev>
==============================

same (??)

Regards
Yogeeraj

[Michael Tully]

You can use the 'lssf' command to see what driver is being used for what terminal type.

Let's try these examples:
# lssf /dev/console
pseudo driver cn minor 0x000000 /dev/console
# lssf /dev/ttyd2a1 (modem)
pci_mux0 card instance 2 port a1 callin at address 0/4/0/0 /dev/ttyd2a1

# pty
/dev/pts/tGb
# lssf /dev/pts/tGb
pseudo driver tels minor 0x00005e /dev/pts/tGb

[j773303]

AS below, could it be possible modify the
permission and own group for tty?

crw--w---- 2 john tty 17 0x00001a Dec 9 03:45 ttyqa

crw-rw-rw- 2 bin tty 17 0x00001a Dec 9 03:45 ttyqa