Add Show Used And Available System Memory as a Linux TIL

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1289 TILs and counting..._
+_1290 TILs and counting..._
 
 ---
 
@@ -502,6 +502,7 @@ _1289 TILs and counting..._
 - [Configure Your Server Timezone](linux/configure-your-server-timezone.md)
 - [List The Statuses Of All Upstart Jobs](linux/list-the-statuses-of-all-upstart-jobs.md)
 - [Show Current System Time And Settings](linux/show-current-system-time-and-settings.md)
+- [Show Used And Available System Memory](linux/show-used-and-available-system-memory.md)
 - [Upgrading Ubuntu](linux/upgrading-ubuntu.md)
 
 ### Mac

linux/show-used-and-available-system-memory.md

@@ -0,0 +1,24 @@
+# Show Used And Available System Memory
+
+The `free` command will display the total RAM on your system as well as how
+much of it is used and how much is still freely available.
+
+```bash
+$ free
+              total        used        free      shared  buff/cache   available
+Mem:        1000260      166004      552808       14440      281448      664724
+Swap:             0           0           0
+```
+
+The default output format of `free` is not very readable though. To make it
+more human readable, you can add the `-h` (_human_) and `--si` (_International
+System of Units_) flags.
+
+```bash
+$ free -h --si
+              total        used        free      shared  buff/cache   available
+Mem:           976M        162M        547M         14M        266M        649M
+Swap:            0B          0B          0B
+```
+
+See `man free` for more details.