The file ttys contains information that is used by various routines to initialize and control the use of terminal special files. This information is read with the getttyent(3) library routines. There is one line in the ttys file per special device file. Fields are separated by tabs and/or spaces. Fields comprised of more than one word should be enclosed in double quotes ("). Blank lines and comments may appear anywhere in the file; comments are delimited by hash marks (#) and new lines. Any unspecified fields will default to null.
The first field is normally the name of the terminal special file as it is found in /dev. However, it can be any arbitrary string when the associated command is not related to a tty.
The second field of the file is the command to execute for the line, usually getty(8), which initializes and opens the line, setting the speed, waiting for a user name and executing the login(1) program. It can be, however, any desired command, for example the start up for a window system terminal emulator or some other daemon process, and can contain multiple words if quoted.
The third field is the type of terminal usually connected to that tty line, normally the one found in the termcap(5) data base file. The environment variable TERM is initialized with the value by either getty(8) or login(1).
The remaining fields set flags in the ty_status entry (see getttyent(3)), specify a window system process that init(8) will maintain for the terminal line, optionally determine the type of tty (whether dialin, network or otherwise), or specify a tty group name that allows the login class database (see login.conf(5)) to refer to many ttys as a group, to selectively allow or deny access or enable or disable accounting facilities for ttys as a group.
As flag values, the strings on and off specify that init(8) should (should not) execute the command given in the second field, while secure (if on is also specified) allows users with a uid of 0 to login on this line. The flag dialin indicates that a tty entry describes a dialin line, and network indicates that a tty entry provides a network connection. Either of these strings may also be specified in the terminal type field. The string window= may be followed by a quoted command string which init(8) will execute before starting the command specified by the second field.
The string group= may be followed by a group name comprised of alphanumeric characters that can be used by login.conf(5) to refer to many tty lines as a group to enable or disable access and accounting facilities. If no group is specified, then the tty becomes a member of the group "none". For backwards compatibility, the group= should appear last on the line, immediately before the optional comment.
Both the second field and any command specified with window= will be split into words and executed using execve(2). Words are separated by any combinations of tabs and spaces. Arguments containing whitespace should be enclosed in single quotes (). Note that no shell-style globbing or other variable substitution occurs.