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free指令是查看Linux类系统物理分区和swap分区的常用指令，是每个从事Linux相关工作的必备技能之一。

free指令帮助手册

如下为free指令的帮助手册。

FREE(1)                                              User Commands                                             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
                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, --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  num‐
              ber 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).
procps-ng                                             2018-05-31                                               FREE(1)