free Command Examples and Usages

The free command provides information about the total amount of the physical and swap memory, as well as the free and used memory. You can learn more with free command examples in this simple guide and other Linux command Lines.

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 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.

free Command Examples

shais@ENL:~$ free -th
              total        used        free      shared  buff/cache   available
Mem:           14Gi       3.0Gi       9.1Gi       335Mi       2.8Gi        11Gi
Swap:         7.4Gi          0B       7.4Gi
Total:         22Gi       3.0Gi        16Gi