mjhjmtu

I want to display free memory as a percentage. I'm pretty sure that I'm not displaying the free memory but the used one. Or am I wrong?

mem=`free -m | awk 'NR ==2printf $3,$2,$3*100/$2'`
echo $mem

Try this,

free | awk '/^Mem/ a=(($3-$7)/$2 * 100); print a"% of Memory used" '
3.43143% of Memory used

free | awk '/^Mem/ a=(($4+$7)/$2 * 100); print a"% of Memory free" '
96.5662% of Memory free

free | awk '/^Mem/ a=(($7)/$2 * 100); print a"% of Memory cached" '
80.4204% of Memory cached

Note: crosscheck the values with glances

If you want to display the amount of free memory as a percentage, Divide Column 4 (free) by Column 2 (total) and multiply the result by 100.

For example:

[user@localhost ~]$ free | awk '/^Mem/ printf("free: %.2f %n", $4/$2 * 100.0) '
free: 97.32 %

If you want to show the amount used, you can divide column 3 (used) by column 2 (total) and multiply the result by 100.

[user@localhost ~]$ free | awk '/^Mem/ printf("Used: %.2f %n", $3/$2 * 100.0) '
Used: 2.75 %

You can use %g for rounding to a specified number of significant digits.

For example, if you only want a whole number, and not a floating point value, you can change the number of floating point digits specified to 0 (zero). In this first example %.2f means 2 floating point values.

And here is an example with zero floating point values:

[user@localhost ~]$ free | awk '/^Mem/ printf("Used: %.0f %n", $3/$2 * 100.0) '
Used: 3 %

This is also answered here:

https://stackoverflow.com/questions/10585978/linux-command-for-percentage-of-memory-that-is-free