Vmstat

vmstat ("virtual memory statistics") is a computer system monitoring tool that collects and displays summary information about operating system memory, processes, interrupts, paging and block I/O. Users of codice_1 can specify a sampling interval which permits observing system activity in near-real time.
The vmstat tool is available on most Unix and Unix-like operating systems, such as FreeBSD, Linux or Solaris.
Syntax.
The syntax and output of vmstat often differs slightly between different operating systems.
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
 r b swpd free buff cache si so bi bo in cs us sy id wa
 0 0 2536 21496 185684 1353000 0 0 0 14 1 2 0 0 100 0
 0 0 2536 21496 185684 1353000 0 0 0 28 1030 145 0 0 100 0
 0 0 2536 21496 185684 1353000 0 0 0 0 1026 132 0 0 100 0
 0 0 2536 21520 185684 1353000 0 0 0 0 1033 186 1 0 99 0
 0 0 2536 21520 185684 1353000 0 0 0 0 1024 141 0 0 100 0
 0 0 2536 21584 185684 1353000 0 0 0 0 1025 131 0 0 100 0
In the above example the tool reports every two seconds for six iterations.
We can get the customized or required outputs by using various options with vmstat command.