One-liners

Sometimes one-liners are so cool, you just want to remember them. And good one-liners can also teach you the intricacies and features of the Bash shell.

Free Memory

Use echo to output the result of a sub-shell, and a few extra characters (' - + p'), which is then piped to the (reverse-polish) desk calculator. Concatenate the /proc/meminfo file, printing it on STDOUT. Using extended-regex grep, we search for lines of output that begin with "MemFree", "Cached" or "Writeback" followed by the colon character. Piping to awk, we can print out the string in position 2 of each line. Those values are ultimately processed in the calculator by popping the last two numbers off the stack (Writeback and Cached), and adding that result to the first number (MemFree).

echo $(cat /proc/meminfo | egrep '^(MemFree|Cached|Writeback):' | awk '{print $2}') - + p | dc

Result:

3033240

Size of X

Since everything is a file, we can look in the folder for processes (/proc), and specifically the folder created for the process id of "X" (X-org). grepping for the line starting with 'VmSize', we can see the Virtual Memory size of our graphical desktop.

grep ^VmSize /proc/$(pidof X)/status

Result:

VmSize:   158212 kB