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
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, --countcount
Display the result
count
times. Requires the
-s
option.
-l, --lohi
Show detailed low and high memory statistics.
-s, --secondsdelay
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.