free(1) — Linux manual page


FREE(1)                         User Commands                        FREE(1)

NAME         top

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

SYNOPSIS         top

       free [options]

DESCRIPTION         top

       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

       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)

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

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

              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, available on kernels 3.14, emulated on kernels
              2.6.27+, otherwise the same as free)

OPTIONS         top

       -b, --bytes
              Display the amount of memory in bytes.

       -k, --kibi
              Display the amount of memory in kibibytes.  This is the

       -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

       -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         top

              memory information

BUGS         top

       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

SEE ALSO         top

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

COLOPHON         top

       This page is part of the procps-ng (/proc filesystem utilities)
       project.  Information about the project can be found at 
       ⟨⟩.  If you have a bug report for
       this manual page, see
       This page was obtained from the project's upstream Git repository
       ⟨⟩ on 2020-09-18.  (At that
       time, the date of the most recent commit that was found in the repos‐
       itory was 2020-09-16.)  If you discover any rendering problems in
       this HTML version of the page, or you believe there is a better or
       more up-to-date source for the page, or you have corrections or
       improvements to the information in this COLOPHON (which is not part
       of the original manual page), send a mail to

procps-ng                        2018-05-31                          FREE(1)

Pages that refer to this page: htop(1)pcp-free(1)slabtop(1)top(1)w(1)proc(5)procfs(5)tmpfs(5)vmstat(8)