free man page

free — Display amount of free and used memory in the system

TL;DR

free

free {{-b/-k/-m/-g}}

free -h

free -s {{X}}

Synopsis

free [options]

Description

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, available on kernels 2.6.32, displayed as zero if not available)

buffers

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

cache

Memory used by the page cache and slabs (Cached and Slab 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)

Options

-b, --bytes

Display the amount of memory in bytes.

-k, --kilo

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

-m, --mega

Display the amount of memory in megabytes.

-g, --giga

Display the amount of memory in gigabytes.

--tera

Display the amount of memory in terabytes.

-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
  K = kilos
  M = megas
  G = gigas
  T = teras

If unit is missing, and you have petabyte of RAM or swap, the number is in terabytes 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 seconds

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

--si

Use power of 1000 not 1024.

-t, --total

Display a line showing the column totals.

--help

Print help.

-V, --version

Display version information.

Files

/proc/meminfo

memory information

See Also

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

Authors

Written by Brian Edmonds.

Reporting Bugs

Please send bug reports to procps@freelists.org

Referenced By

dstat(1), freecolor(1), htop(1), pcp-free(1), proc(5), procinfo(8), procinfo-ng(8), slabtop(1), smem(8), tmpfs(5), top(1), vmstat(8), w(1).

July 2014 procps-ng User Commands