There is one line in the ttys file per special file. Fields are separated by tabs and/or spaces. Some fields may contain more than one word and should be enclosed in double quotes. Blank lines and comments can appear anywhere in the file; comments are delimited by `#' and new line. Unspecified fields default to null.
The first field is the terminal's entry in the device directory, /dev.
The second field of the file is the command to execute for the line, typically getty(8), which performs such tasks as baud-rate recognition, reading the login name, and calling login(1). 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. It's an error to specify a command instead of `none' for a pseudo-tty such as ttyp0.
The third field is the type of terminal normally connected to that tty line, as found in the termcap(5) data base file.
The remaining fields set flags in the ty_status entry (see getttyent(3)) or specify a window system process that init(8) will maintain for the terminal line. As flag values, the strings `on' and `off' specify whether or not init should execute the command given in the second field (it's an error to specify `on' if the second field contains the string `none' rather than a command). The string `secure' in addition to `on' allows root to login on this line. These flag fields should not be quoted.
The string `window=' is followed by a quoted command string which init will execute before starting getty. If the line ends in a comment, the comment is included in the ty_comment field of the ttyent structure.
Some examples:
console "/etc/getty std.1200" vt100 on secure ttyd0 "/etc/getty d1200" dialup on # 555-1234 ttyh0 "/etc/getty std.9600" hp2621-nl on # 254MC ttyh1 "/etc/getty std.9600" plugboard on # John's office ttyp0 none network ttyp1 none network ttyv0 "/usr/new/xterm -L :0" vs100 on window="/usr/new/Xvs100 0"
The first example permits root login on the console at 1200 baud, the second allows dialup at 1200 baud without root login, the third and fourth allow login at 9600 baud with terminal types of "hp2621-nl" and "plugboard" respectively, the fifth and sixth line are examples of network pseudo ttys, which should not have getty enabled on them, and the last example shows a terminal emulator and window system startup entry.