free

Display system memory

$ free

$ free -[b|k|m|g]

$ free -h

$ free -s [2]

free [options]

free displays the total amount of free and used physical and swap memory in the system, as well as the buffers and caches used by the kernel. The information is gathered by parsing /proc/meminfo. The displayed columns are:

total

Total installed memory (MemTotal and SwapTotal in /proc/meminfo)

used

Used memory (calculated as total - free - buffers - cache)

free

Unused memory (MemFree and SwapFree in /proc/meminfo)

shared

Memory used (mostly) by tmpfs (Shmem in /proc/meminfo)

buffers

Memory used by kernel buffers (Buffers in /proc/meminfo)

cache

Memory used by the page cache and slabs (Cached and SReclaimable in /proc/meminfo)

buff/cache

Sum of buffers and cache

available

Estimation of how much memory is available for starting new applications, without swapping. Unlike the data provided by the cache or free fields, this field takes into account page cache and also that not all reclaimable memory slabs will be reclaimed due to items being in use (MemAvailable in /proc/meminfo, available on kernels 3.14, emulated on kernels 2.6.27+, otherwise the same as free)

-b, --bytes

Display the amount of memory in bytes.

-k, --kibi

Display the amount of memory in kibibytes. This is the default.

-m, --mebi

Display the amount of memory in mebibytes.

-g, --gibi

Display the amount of memory in gibibytes.

--tebi

Display the amount of memory in tebibytes.

--pebi

Display the amount of memory in pebibytes.

--kilo

Display the amount of memory in kilobytes. Implies --si.

--mega

Display the amount of memory in megabytes. Implies --si.

--giga

Display the amount of memory in gigabytes. Implies --si.

--tera

Display the amount of memory in terabytes. Implies --si.

--peta

Display the amount of memory in petabytes. Implies --si.

-h, --human

Show all output fields automatically scaled to shortest three digit unit and display the units of print out. Following units are used.

  B = bytes
  Ki = kibibyte
  Mi = mebibyte
  Gi = gibibyte
  Ti = tebibyte
  Pi = pebibyte

If unit is missing, and you have exbibyte of RAM or swap, the number is in tebibytes and columns might not be aligned with header.

-w, --wide

Switch to the wide mode. The wide mode produces lines longer than 80 characters. In this mode buffers and cache are reported in two separate columns.

-c, --count count

Display the result count times. Requires the -s option.

-l, --lohi

Show detailed low and high memory statistics.

-s, --seconds delay

Continuously display the result delay seconds apart. You may actually specify any floating point number for delay using either . or , for decimal point. usleep(3) is used for microsecond resolution delay times.

--si

Use kilo, mega, giga etc (power of 1000) instead of kibi, mebi, gibi (power of 1024).

-t, --total

Display a line showing the column totals.

--help

Print help.

-V, --version

Display version information.

/proc/meminfo

memory information

The value for the shared column is not available from kernels before 2.6.32 and is displayed as zero.

Please send bug reports to

ps(1), slabtop(1), top"(1), vmstat(8).