How can I check if swap is active from the command line?

Question

How can I check if swap is active, and which swap devices are set up, on the command line?

Answer 1

in linux, you can use

• cat /proc/meminfoto see total swap, and free swap (all linux)
• cat /proc/swaps to see which swap devices are being used (all linux)
• swapon -s to see swap devices and sizes (where swapon is installed)
• vmstat for current virtual memory statistics

in Mac OS X, you can use

• vm_stat to see information about virtual memory (swap)
• ls -lh /private/var/vm/swapfile* to see how many swap files are being used.

in Solaris, you can use

• swap -l to see swap devices/files, and their sizes
• swap -s to see total swap size, used & free
• vmstat to see virtual memory statistics

On some systems, "virtual memory" refers only to disk-backed memory devices, and on other systems, like Solaris, Virtual Memory can refer to any user process address space, including tmpfs filesystems (like /tmp) and shared memory space.

Answer 2

Try swapon -s for a list of current swap devices and other relevant information.