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free Command in Linux
NAME
free Display amount of free and used memory in the system
SYNOPSIS
free [-b | -k | -m] [-o] [-s delay ] [-t] [-l] [-V]
DESCRIPTION
free displays the total amount of free and used physical and swap memory in the system, as well as the buffers used by the kernel. The shared memory column should be ignored; it is obsolete.OPTIONS
| TAG | DESCRIPTION |
|---|---|
| -b | The -b switch displays the amount of memory in bytes; the -k switch (set by default) displays it in kilobytes; the -m switch displays it in megabytes. |
| -t | The -t switch displays a line containing the totals. |
| -o | The -o switch disables the display of a "buffer adjusted" line. If the -o option is not specified, free subtracts buffer memory from the used memory and adds it to the free memory reported |
| -s | The -s switch activates continuous polling delay seconds apart. You may actually specify any floating point number for delay, usleep(3) is used for microsecond resolution delay times. |
| -l | The -l switch shows detailed low and high memory statistics |
| -V | The -V switch displays version information. |
| x | Extract members (named member) from the freechive. You can use the v modifier with this operation, to request that free list each name as it extracts it.
If you do not specify a member, all files in the freechive freee extracted. Files cannot be extracted from a thin freechive. |
EXAMPLES
EXAMPLE-1:
Free command used to check the used and available space of physical memory and swap memory in KB.
# free
output:
# free
total used free shared buffers cached
Mem: 1000192 465672 534520 176 55088 175212
-/+ buffers/cache: 235372 764820
Swap: 1044476 12372 1032104
EXAMPLE-2:
Free command with option -b, display the size of memory in Bytes.
# free -b
output:
# free -b
total used free shared buffers cached
Mem: 1024196608 476831744 547364864 180224 56418304 179400704
-/+ buffers/cache: 241012736 783183872
Swap: 1069543424 12668928 1056874496
EXAMPLE-3:
Free command with option -k, display the size of memory in (KB) Kilobytes.
# free -k
output:
# free -k
total used free shared buffers cached
Mem: 1000192 465640 534552 176 55096 175196
-/+ buffers/cache: 235348 764844
Swap: 1044476 12372 1032104
EXAMPLE-4:
To see the size of the memory in (MB) Megabytes use option as -m.
# free -m
output:
# free -m
total used free shared buffers cached
Mem: 976 454 522 0 53 171
-/+ buffers/cache: 229 746
Swap: 1019 12 1007
EXAMPLE-5:
Using -g option with free command, would display the size of the memory in GB(Gigabytes)
# free -g
output:
# free -g
total used free shared buffers cached
Mem: 0 0 0 0 0 0
-/+ buffers/cache: 0 0
Swap: 0 0 0
EXAMPLE-6:
Free command with -t option, will list the total line at the end.
# free -t
output:
# free -t
total used free shared buffers cached
Mem: 1000192 465640 534552 176 55096 175196
-/+ buffers/cache: 235348 764844
Swap: 1044476 12372 1032104
Total: 2044668 478012 1566656
EXAMPLE-7:
By default the free command display “buffer adjusted” line, to disable this line use option as -o
# free -o
output:
# free -o
total used free shared buffers cached
Mem: 1000192 465640 534552 176 55096 175196
Swap: 1044476 12372 1032104
EXAMPLE-8:
The -s option with number, used to update free command at regular intervals.
# free -s 5
This command displays output every 5 seconds.
output:
# free -s 5
total used free shared buffers cached
Mem: 1000192 465640 534552 176 55096 175196
-/+ buffers/cache: 235348 764844
Swap: 1044476 12372 1032104
total used free shared buffers cached
Mem: 1000192 465656 534536 176 55096 175196
-/+ buffers/cache: 235364 764828
Swap: 1044476 12372 1032104
total used free shared buffers cached
Mem: 1000192 465656 534536 176 55096 175196
-/+ buffers/cache: 235364 764828
Swap: 1044476 12372 1032104
EXAMPLE-9:
* The -l switch displays detailed high and low memory size statistics.
# free -l
output:
# free -l
total used free shared buffers cached
Mem: 1000192 465640 534552 176 55096 175196
Low: 1000192 465640 534552
High: 0 0 0
-/+ buffers/cache: 235348 764844
Swap: 1044476 12372 1032104