17.7 Terminals and Modems

   

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Terminals and modems are serial devices and are connected to a serial port or an MUX. The device files for these are placed directly under the /dev directory (not in a subdirectory). Each terminal device file starts with tty followed by an MUX number. The next letter is " p " followed by a port number on the MUX. For example, a device file /dev/tty0p3 represents a terminal on port 3 of the first MUX.

Pseudoterminal device files are used by applications that use terminal emulation and network services. These device files are found in pairs of master and slave files. The master files are found in /dev/ptym with a name starting with pty . These are linked to files with the same name in the /dev directory. The slave files are found in the /dev/pty directory, and their names start with tty . These are also linked to files in the /dev directory with the same name. The stream-based pseudoterminal files are present in the /dev/pts directory.

By default, 60 pseudoterminal device files are present. You can increase the number of pseudoterminals using the insf command. The following command creates 90 pseudoterminal device files.

 insf -e -n 90 -d ptym 

A modem is represented by three device files. Files for a modem attached to port number 4 of the first MUX are:

 /dev/cua0p4 /dev/cul0p4 /dev/ttyd0p0 

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