Free Command in Linux with Examples
free Command
The free command provides information about unused and used memory and swap space on any computer running Linux or another Unix-like operating system.
Syntax
free (option)
OPTIONS
free -b = bytes
free -k = kilo bytes
free -m = mega bytes
free -g = giga bytes
free -tera = tera bytes
free -h = human readable
free -o = old model (it means not shows buffers)
free -t = total (it shows total in last line)
free -c = count time (it require S option)
free -s = seconds (you can set delay seconds using S)
free -V = check the version
Display the physical memory in KB
Free command used to check the used and available space of physical memory and swap memory in (KB).
[root@linuxhelp ~]# free
total used free shared buffers cached
Mem: 7958716 7243892 714824 455924 760448 2126940
-/+ buffers/cache: 4356504 3602212
Swap: 16383996 121776 16262220
Display the physical memory in bytes
If you want to display the size of memory in Bytes, use free command with option -b
[root@linuxhelp ~]# free -b
total used free shared buffers cached
Mem: 8149725184 7409377280 740347904 475836416 778936320 2182283264
-/+ buffers/cache: 4448157696 3701567488
Swap: 16777211904 125743104 16651468800
Display the physical memory in Mega bytes
If you want to see the size of the memory in (MB) Megabytes use option as -m.
[root@linuxhelp ~]# free -m
total used free shared buffers cached
Mem: 7772 7053 719 424 743 2051
-/+ buffers/cache: 4258 3513
Swap: 15999 119 15880
Display the physical memory in Giga bytes
With help of using option &ndash g in free command the result will became size of the memory in GB.
[root@linuxhelp ~]# free -g
total used free shared buffers cached
Mem: 7 6 0 0 0 2
-/+ buffers/cache: 4 3
Swap: 15 0 15
Display the physical memory in total KB with last line
Free command with -t option, will list the total memory in (KB)
[root@linuxhelp ~]# free -t
total used free shared buffers cached
Mem: 7958716 7194132 764584 425560 762100 2090692
-/+ buffers/cache: 4341340 3617376
Swap: 16383996 122796 16261200
Total: 24342712 7316928 17025784
Display the physical memory in total MB with last line
Free command with -mt option, will list the total memory in (MB)
[root@linuxhelp ~]# free -mt
total used free shared buffers cached
Mem: 7772 7054 717 440 744 2065
-/+ buffers/cache: 4244 3527
Swap: 15999 119 15880
Total: 23772 7174 16597
Display the physical memory in total GB with last line
Free command with -gt option, will list the total memory in (GB) at the end of the output
[root@linuxhelp ~]# free -gt
total used free shared buffers cached
Mem: 7 6 0 0 0 2
-/+ buffers/cache: 4 3
Swap: 15 0 15
Total: 23 7 16
Display the physical memory in old model
Using option -o with free would display only the PHYSICAL MEMORY and SWAP, it will disabled showing buffer and cache.
[root@linuxhelp ~]# free -o
total used free shared buffers cached
Mem: 7958716 7214032 744684 432888 762968 2097284
Swap: 16383996 122784 16261212
Display the physical memory in old model in MB
Free command with -mt option, will list the total memory in (MB) at the end of the output
[root@linuxhelp ~]# free -om
total used free shared buffers cached
Mem: 7772 7004 768 415 745 2040
Swap: 15999 119 15880
Display the physical memory in old model in GB
Free command with using -og option,would display PHYSICAL MEMORY and SWAP only in GB type.
[root@linuxhelp ~]# free -og
total used free shared buffers cached
Mem: 7 6 0 0 0 2
Swap: 15 0 15
Display the physical memory in old model in GB with total memory
Free command with using -ogt option,would display PHYSICAL MEMORY in GB type with total memory.
[root@linuxhelp ~]# free -ogt
total used free shared buffers cached
Mem: 7 6 0 0 0 2
Swap: 15 0 15
Total: 23 7 16
Display the physical memory usage in some regular time interval period
Using option &ndash s with numbers to update free command in regular intervals.
[root@linuxhelp ~]# free -s 5
total used free shared buffers cached
Mem: 7958716 7174232 784484 437272 764240 2099472
-/+ buffers/cache: 4310520 3648196
Swap: 16383996 122784 16261212
total used free shared buffers cached
Mem: 7958716 7175664 783052 437912 764240 2100112
-/+ buffers/cache: 4311312 3647404
Swap: 16383996 122784 16261212
total used free shared buffers cached
Mem: 7958716 7162100 796616 423060 764244 2085260
-/+ buffers/cache: 4312596 3646120
Swap: 16383996 122784 16261212
Display the physical memory usage in some regular time interval period in MB
[root@linuxhelp ~]# free -ms 5
total used free shared buffers cached
Mem: 7772 7011 760 422 746 2045
-/+ buffers/cache: 4218 3553
Swap: 15999 119 15880
total used free shared buffers cached
Mem: 7772 7012 759 421 746 2045
-/+ buffers/cache: 4220 3552
Swap: 15999 119 15880
total used free shared buffers cached
Mem: 7772 7013 759 422 746 2045
-/+ buffers/cache: 4220 3551
Swap: 15999 119 15880
Display the physical memory usage in some regular time interval period in MB with counts
To display the physical memory usage for every 5 seconds in MB with count as 3 execute the below command.
[root@linuxhelp ~]# free -ms 5 -c 3
total used free shared buffers cached
Mem: 7772 7030 741 431 747 2055
-/+ buffers/cache: 4228 3544
Swap: 15999 119 15880
total used free shared buffers cached
Mem: 7772 7013 758 413 747 2037
-/+ buffers/cache: 4229 3542
Swap: 15999 119 15880
total used free shared buffers cached
Mem: 7772 7022 749 422 747 2045
-/+ buffers/cache: 4229 3542
Swap: 15999 119 15880
To check the free version
Free using option -V, will display free command version
[root@linuxhelp ~]# free -V
procps version 3.2.8
Display the physical memory in current running process in KB size with total memory
To display the physical memory usage in current running process with total memory in KB execute the below command.
[root@linuxhelp ~]# watch free -t
Every 2.0s: free -t Sat Feb 20 17:19:24 2016
total used free shared buffers cached
Mem: 16363608 3645152 12718456 107404 103348 757088
-/+ buffers/cache: 2784716 13578892
Swap: 32767996 0 32767996
Total: 49131604 3645152 45486452