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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | FILES | BUGS | SEE ALSO | COLOPHON |
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FREE(1) General Commands Manual FREE(1)
free - Display amount of free and used memory in the system
free [option ...]
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 usable memory (MemTotal and SwapTotal in
/proc/meminfo). This includes the physical and swap memory
minus a few reserved bits and kernel binary code.
used Used or unavailable memory (calculated as total -
available)
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)
-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.
-L, --line
Show output on a single line, often used with the -s option
to show memory statistics repeatedly.
-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.
-v, --committed
Display a line showing the memory commit limit and amount
of committed/uncommitted memory. The total column on this
line will display the memory commit limit. This line is
relevant if memory overcommit is disabled.
--help Print help.
-V, --version
Display version information.
/proc/meminfo
memory information
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 ⟨[email protected]⟩.
ps(1), slabtop(1), top(1), vmstat(8).
This page is part of the procps-ng (/proc filesystem utilities)
project. Information about the project can be found at
⟨https://gitlab.com/procps-ng/procps⟩. If you have a bug report
for this manual page, see
⟨https://gitlab.com/procps-ng/procps/blob/master/Documentation/bugs.md⟩.
This page was obtained from the project's upstream Git repository
⟨https://gitlab.com/procps-ng/procps.git⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-07-30.) 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
[email protected]
procps-ng 2023-05-02 FREE(1)
Pages that refer to this page: htop(1), pcp-free(1), slabtop(1), top(1), w(1), proc(5), proc_meminfo(5), tmpfs(5), vmstat(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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