Wednesday, April 23, 2008

Process Control commands

ps (=print status)
Display the list of currently running processes with their process IDs (PID) numbers. Use ps axu to see all processes currently running on your system (also those of other users or without a controlling terminal), each with the name of the owner. Use "top" to keep listing the processes currently running.

fg PID
Bring a background or stopped process to the foreground.

bg PID
Send the process to the background. Opposite to fg. The same can be accomplished with z. If you have stopped jobs, you have to type exit twice in row to log out.

Run any command in the background (the symbol "&" means "run the proceeding command in the background").

batch any_command
Run any command (usually one that is going to take more time) when the system load is low. I can logout, and the process will keep running.

at 17:00
Execute a command at a specified time. You will be prompted for the command(s) to run, until you press d.

kill PID
Force a process shutdown. First determine the PID of the process to kill using ps.

killall program_name
Kill program(s) by name.

xkill (in an xwindow terminal)
Kill a GUI-based program with mouse. (Point with your mouse cursor at the window of the process you want to kill and click.)

lpc (as root)
Check and control the printer(s). Type "?" to see the list of available commands.

Show the content of the printer queue. Under KDE (X-Windows), you may use GUI-based "Printer Queue" available from "K"menu-Utilities.

lprm job_number
Remove a printing job "job_number" from the queue.

nice program_name
Run program_name adjusting its priority. Since the priority is not specified in this example, it will be adjusted by 10 (the process will run slower), from the default value (usually 0). The lower the number (of "niceness" to other users on the system), the higher the priority. The priority value may be in the range -20 to 19. Only root may specify negative values. Use "top" to display the priorities of the running processes.

renice -1 PID (as root)
Change the priority of a running process to -1. Normal users can only adjust processes they own, and only up from the current value (make them run slower).

[ctrl]c, [ctrl]z, [ctrl]s, and [ctrl]q also belong to this chapter but they were described
previously. In short they mean: stop the current command, send the current command to the background, stop the data transfer, resume the data transfer.

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