显示系统内存的使用量.实际上他是整理/proc/meminfo的内容显示出来.他的作者是Brian Edmonds.

  1. [root@iZuf6ay9wx8ybghfwlkw6kZ root]# free
  2. total used free shared buff/cache available
  3. Mem: 3881688 837896 138132 444 2905660 2731288
  4. Swap: 0 0 0

已使用内存 + 内换内存.

已使用内存 (calculated as total - free - buffers - cache).

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 /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)


-b, —bytes

-k, —kilo
以千字节为单为来显示. (默认).

-m, —mega

-g, —giga

—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.

  1. B = bytes
  2. K = kilos
  3. M = megas
  4. G = gigas
  5. T = teras
  6. If unit is missing, and you have petabyte of RAM or swap, the number is in terabytes 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 seconds
Continuously display the result delay seconds apart. You may actually specify any floating point number for delay, usleep(3) 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.