free reports the amount of free and used memory in the system, both physical and swap memory. kill is used to send signals to processes. ps gives a snapshot of the current processes. pgrep looks up processes based on their name and other attributes. pkill signals processes based on their name and other attributes. skill sends signals to processes matching the given criteria. snice changes the scheduling priority of processes matching the given criteria. sysctl modifies kernel parameters at run time. tload prints a graph of the current system load average. top displays the top CPU processes. It provides an ongoing look at processor activity in real time. vmstat reports virtual memory statistics, giving information about processes, memory, paging, block IO, traps, and CPU activity. w shows which users are currently logged on, where and since when. watch runs a given command repeatedly, displaying the first screenful of its output. This allows you to watch the output change over time. libproc contains the functions used by most programs in this package.