free Man page

FREE(1) User Commands FREE(1)


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


free [options]


free displays the total amount of free and used physical and swap mem‐
ory in the system, as well as the buffers and caches used by the ker‐
nel. The information is gathered by parsing /proc/meminfo. The dis‐
played 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)

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

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

Sum of buffers and cache

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, avail‐
able 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, –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

-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
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.

memory information


ps, slabtop, top, vmstat(8).

Written by Brian Edmonds.


Please send bug reports to ⟨⟩

procps-ng July 2014 FREE(1)