Add Detect If You Are On A Mac as a vim til

Author: jbranchaud

README.md

@@ -10,7 +10,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 For a steady stream of TILs from a variety of rocketeers, checkout
 [til.hashrocket.com](https://til.hashrocket.com/).
 
-_548 TILs and counting..._
+_549 TILs and counting..._
 
 ---
 
@@ -561,6 +561,7 @@ _548 TILs and counting..._
 - [Delete To The End Of The Line](vim/delete-to-the-end-of-the-line.md)
 - [Deleting Buffers In BufExplorer](vim/deleting-buffers-in-bufexplorer.md)
 - [Deleting Directories Of Files From netrw](vim/deleting-directories-of-files-from-netrw.md)
+- [Detect If You Are On A Mac](vim/detect-if-you-are-on-a-mac.md)
 - [Difference Between :wq and :x](vim/difference-between-wq-and-x.md)
 - [Display Word Count Stats](vim/display-word-count-stats.md)
 - [Edges Of The Selection](vim/edges-of-the-selection.md)

vim/detect-if-you-are-on-a-mac.md

@@ -0,0 +1,24 @@
+# Detect If You Are On A Mac
+
+There are a couple ways of detecting with vimscript if you are on a mac.
+This can be useful if you are writing a plugin with OS-specific
+functionality. Here are two ways to make that check.
+
+```vimscript
+if has('macunix') || has('mac') || has('osx')
+  ...
+endif
+```
+
+Alternatively, you can use Vim's `system()` function to execute unix's
+`uname` command. This command will give you the name of the operating
+system. In the event you are using a Mac, the result of `uname` should be
+`Darwin`. The following regex match is a good way to make this check.
+
+```vimscript
+if system('uname') =~ "Darwin"
+  ...
+endif
+```
+
+See `:h has()`, `:h system()`, and `man uname` for more details.