STREAMS-based job control

Job Control requires support from a line discipline module on the controlling terminal's Stream. The TCSETA, TCSETAW, and TCSETAF commands of termio(7) allow a process to set the following line discipline values relevant to Job Control:

SUSP character

A user defined character that, when typed, causes the line discipline module to request that the Stream head sends a SIGTSTP signal to the foreground process with an M_PCSIG message, which by default stops the members of that group. If the value of SUSP is zero, the SIGTSTP signal is not sent, and the SUSP character is disabled.

TOSTOP flag

If TOSTOP is set, background processes are inhibited from writing to their controlling terminal.

A line discipline module must record the SUSP suspend character and notify the Stream head when the user has typed it, and record the state of the TOSTOP bit and notify the Stream head when the user has changed it.