UNIX is a flexible, open system that is multi-user and multi-tasking.

because of the multi-user aspect, serial communications is built into the UNIX system as every user must communicate with the system from a terminal connected with a serial line,

when a call is received, the getty program answers it at the baud rate specified in gettydefs (the data file that contains the line settings and terminal types associated with all the ports on the system) and prints "login:" on the terminal

the ttymgmt program is used to modify the system configuration when terminals are added or changed, the ttymgmt alters the lines in gettydefs to store the changes made...... although you could "manually" edit gettydefs this is NOT recommended since it is easy to make mistakes and most users are not familiar with the cryptic form in which the information is stored.

Programs like ttymgmt are referred to as user agents since they make complex changes to the data files in the operating system on behalf of the user, while hiding this complexity from the user.

It should be noted that only the terminal type is stored in gettydefs, the actual capabilities of that terminal type are stored in terminfo.

Also the ttymgmt program can be invoked from the sysadm menu.

© copyright 2002 Stephen E. Mendes, Barbados.

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