How to get memory used(RAM used) using Linux command?
I am trying to retrieve memory used(RAM) in percentage using Linux commands. My cpanel shows Memory Used which I need to display on a particular webpage.
From forums, I found out that correct memory can be found from the following:
free -m
Result:
-/+ buffers/cache: 492 1555
-/+ buffers/cache: contains the correct memory usage. I don’t know how to parse this info or if there is any different command to get the memory used in percentage.
Here is sample output from free:
% free
total used free shared buffers cached
Mem: 24683904 20746840 3937064 254920 1072508 13894892
-/+ buffers/cache: 5779440 18904464
Swap: 4194236 136 4194100
The first line of numbers (Mem:) lists
totalmemoryusedmemoryfreememory- usage of
shared - usage of
buffers - usage filesystem caches (
cached)
In this line used includes the buffers and cache and this impacts free.
This is not your “true” free memory because the system will dump cache if needed to satisfy allocation requests.
The next line (-/+ buffers/cache:) gives us the actual used and free memory as if there were no buffers or cache.
The final line (Swap) gives the usage of swap memory. There is no buffer or cache for swap as it would not make sense to put these things on a physical disk.
To output used memory (minus buffers and cache) you can use a command like:
% free | awk 'FNR == 3 {print $3/($3+$4)*100}'
23.8521
This grabs the third line and divides used/total * 100.
And for free memory:
% free | awk 'FNR == 3 {print $4/($3+$4)*100}'
76.0657
I am going to mention on how to parse the information on free command. To find the percentage, you can use as suggested in the other 2 answers.
This is clearly explained here. I would try to explain from what I have in my system.
free -m
total used free shared buffers cached
Mem: 7869 4402 3466 0 208 3497
-/+ buffers/cache: 696 7173
Swap: 3999 216 3783
Now, let us see what the various numbers actually represent.
Line1
- 7869 Indicates memory/physical RAM available for my machine.
- 4402 Indicates memory/RAM used by my system.
- 3466 Indicates Total RAM free and available for new process to run.
- 0 Indicates shared memory. This column is obsolete and may be removed in future
releases of free. - 208 Indicates total RAM buffered by different applications in Linux.
- 3497 Indicates total RAM used for Caching of data for future purpose.
Line2
-/+ buffers/cache: 696 7173
How to calculate the values 696 and 7173 obtained in Line2?
Total used (4402) – Total buffer RAM (208) – Total RAM for caching(3497) should constitute the Actual used RAM in the system. It returns me 697 which is the actual used RAM output in the second line.
Now, Total Available (7869) – Actual Used (696) should give you the free memory which is 7173 in this case which is also got as output in the second line.
Though a duplicate as pointed by @szboardstretcher , my preference from the solutions (in the original question) is the one below, specially since you want to parse to a webpage.
$ free | awk '/Mem/{printf("used: %.2f%"), $3/$2*100} /buffers/cache/{printf(", buffers: %.2f%"), $4/($3+$4)*100} /Swap/{printf(", swap: %.2f%"), $3/$2*100}'
Output:
used: 82.68%, buffers: 42.81%, swap: 1.27%
free | awk '/Mem/{printf("used: %.2f%"), $3/$2*100} /buffers/cache/{printf(", buffers: %.2f%"), $4/($3+$4)*100} /Swap/{printf(", swap: %.2f%n"), $3/$2*100}'
Adds a new line after the swap number
For upto CentOS 7 You can try
cat /proc/meminfo
to see real usage of memory by processes.
Note, free 3.3 and above does not have a -/+ buffers/cache: line, so the older answers won’t work. In 3.3 free compares used vs availalble in the "Mem" line.
The following will work for both old and new versions of free.
free | awk '$1 == "Mem:" {x= $7/($3+$7)*100} $2 == "buffers/cache:" {x= $4/($3+$4)*100} $1 == "Swap:" {print x}'