free Command:free is the most commonly used command for checking the memory usage of a Linux system. It displays information about the total, used, and free memory.

top Command

The simplest way to check the RAM memory usage is to display the contents of the /proc/meminfo virtual file. This file is used by the free, top, ps , and other system information commands.

ps_mem Script

output in bytes

output in kibibytes

output in mebibytes

 Display System Memory

 Display Memory in Gigabytes

Display Total Line

Display Memory Status for Regular Intervals

Show Low and High Memory Statistics

Check Free Version

Showing the Column Totals

Showing Memory Usage in Other Metrics

by using -h option shows the output in human readable format

by using free command we see the results for total, used and free memory on system by accessing the system kernel. it also displays the shared cache and available 

it will show us onnly one output and this output will be changing at regular intervals

-s option is used to instriuts free command to refresh the puput for every 3 sec. to stop th process ctrl+c

gives the output in mebibytes

use the si the power 1024 and in megabytes

-c option instructs the free command to automatocally quit after refreshing 4 times

to see the buffer and cache colums seperatly

total option instructs free to show the toatal memory of used,free total columns of memory and swap columns

the command produces ouput in mebibytes with 3 seconds delay and quits after refreshing the ouput for 4 times

Output Example:

              total        used        free      shared  buff/cache   available
Mem:        16000000     8000000     4000000      500000     4000000    10000000
Swap:        8000000      2000000     6000000

Explanation:

• Mem: Displays total, used, free, shared, cache, and available memory.
• Swap: Shows swap memory details.

Output Example:

              total        used        free      shared  buff/cache   available
Mem:           16G         8G         4G       500M        4G         10G
Swap:           8G         2G         6G
 

Explanation:
The -h flag makes it human-readable (e.g., GB, MB, KB).

Displays memory in MB (Megabytes).

Displays memory in GB (Gigabytes).

This updates the memory usage every 2 seconds. (Press Ctrl+C to stop.)

Output Example:

              total        used        free      shared  buff/cache   available
Mem:           16G         8G         4G       500M        4G         10G
Swap:           8G         2G         6G
Total:        24G        10G        10G
 

Explanation:
The -t flag adds a "Total" row summing up RAM and swap memory.

This hides swap memory details and only shows physical RAM usage.

MemTotal:       16000000 kB
MemFree:         4000000 kB
MemAvailable:   10000000 kB
SwapTotal:       8000000 kB
SwapFree:        6000000 kB
Explanation:
This provides detailed memory stats beyond what free shows.

This shows memory usage before and after running a program within 10 seconds.

Output Example:

Used Memory: 50.00%
 

Explanation:
This calculates the percentage of used RAM.

Displays system memory usage (total, used, free).