Mac OS X for Unix Geeks

top

The top utility displays memory statistics and a list of running processes. It is divided into two regions: the top region contains memory statistics and the bottom region contains details on each process.

Tip

The Mac OS X version of top is based on the one used in early versions of BSD. It was ported to Mach in 1988, to NeXTSTEP in 1990, and to Mac OS X in 1999.

You can specify the number of processes to show by supplying a numeric argument. By default, top refreshes its display every second and sorts the list of processes by process ID (PID) in descending order. You can set top to sort by CPU utilization with -u, and you can specify the refresh delay with the -s option. Figure 8-1 shows the output of top -u 10 (if you wanted to refresh the output every 3 seconds, you could run top -s3 -u 10).

Figure 8-1. Sample output from top

Table 8-1 describes the values shown in the top region, and Table 8-2 describes the columns in the bottom region (process information).

Table 8-1. Memory information displayed by top

Item number	Item	Description
1	Processes	The number of processes and threads. A running process is currently using CPU time, while a sleeping process is not.
2	Load Avg.	The average system load (number of jobs vying for the CPU’s attention) over the last 1, 5, and 15 minutes.
3	CPU usage	A breakdown of CPU usage, listing time spent in user mode, kernel (