free(1)
NAME
free - Display amount of free and used memory in the system
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)
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)
OPTIONS
-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
K = kibibyte
M = mebibyte
G = gibibyte
T = tebibyte
P = 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.
FILES
/proc/meminfo
memory information
BUGS
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
procps@freelists.org
SEE ALSO
ps(1), slabtop(1), top(1), vmstat(8).
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