updated readme for MAC OSX

README.md

@@ -2,7 +2,7 @@
 Obtain SSL certificates from the letsencrypt.org ACME server.  Suitable for automating the process on remote servers.
 
 ## Features
-* **Bash** - It runs on virtually all linux machines, including MAC OSX.
+* **Bash** - It runs on virtually all linux machines, including MAC OSX (for MAC OSX see the notes at the bottom of the page).
 * **Get certificates for remote servers** - The tokens used to provide validation of domain ownership, and the certificates themselves can be automatically copied to remote servers (via ssh, sftp or ftp for tokens). The script doesn't need to run on the server itself. This can be useful if you don't have access to run such scripts on the server itself, as it's a shared server for example.
 * **Runs as a daily cron** - so certificates will be automatically renewed when required.
 * **Automatic certificate renewals**
@@ -219,6 +219,17 @@ these are available in getssl to check if the certificate is installed correctly
 | port number      |      |              |
 
 
+## MAC OSX
+The date, grep and sed functions on a MAC are different from gnu-bash, and don't have the same functionality - you can install the "standard" linux versions of these though, and they are gdate, ggrep and gsed.
+
+
+```
+brew install grep
+brew install coreutils
+brew install gnu-sed
+```
+should install the relevant items.
+
 ## Issues / problems / help
 If you have any issues, please log them at https://github.com/srvrco/getssl/issues