How to know which ttyS* file is linked to which serial port?

Question

I'm no expert of Linux or serial programming, and my understanding of Linux serial port communication is: the system links certain /dev/ttyS* file to a certain physical serial port, then the system or other procedures can talk with any device that is attached to that serial port via the /dev/ttyS* file. And the /dev/ttyS* file would be assigned/linked to the serial port no matter there's any device attached.

If I'm correct about this, then is there any way, in C, that I can get all such /dev/ttyS* files which are linked to physical serial ports?

Have already searched all over Google and SO, nothing really helpful found, plz halp!

PS, I can find such files by using:

dmesg | grep ttyS

but I need a more precise way to get these info, things like libudev can do this ??

Unknown Unknown · Accepted Answer · 2014-02-27T06:42:49

I'm not absolutely sure what is being asked here, but the way /dev/ttyS* are mapped has not changed in ages and the first serial port, sometimes called with DOS name COM1, is still accessible as /dev/ttyS0, second being /dev/ttyS1 and so on.

From kernel documentation, namely from file Documentation/devices.txt you can still find some useful information:

4 char        TTY devices
              0 = /dev/tty0         Current virtual console

              1 = /dev/tty1         First virtual console
                ...
             63 = /dev/tty63        63rd virtual console
             64 = /dev/ttyS0        First UART serial port
                ...
            255 = /dev/ttyS191      192nd UART serial port

            UART serial ports refer to 8250/16450/16550 series devices.

If your question how to find all serial ports on your system, see /dev/serial which should have (unless you're using a kernel really ancient) entries by-id and by-uuid.

How to know which ttyS* file is linked to which serial port?

1 Answers