Update README.md file

README.md

@@ -1,3 +1,31 @@
 # check_ssl_cert_file
 
-Check plugin for Icinga/Nagios to validate expiration date of a X509 SSL certificate file using OpenSSL
+Check plugin for Icinga/Nagios to validate expiration date of a X509 SSL certificate file using OpenSSL
+
+## Requirement
+
+* OpenSSL
+
+## Usage
+
+```
+Usage : check_ssl_cert_file [cert file path]
+        -f [file]       Specify certificate file path
+        -w [integer]    Specify warning days limit
+        -c [integer]    Specify critial days limit
+        -d              Enable debug mode
+        -h              Show this message
+```
+
+## Copyright
+
+
+Copyright (c) 2017 Benjamin Renard
+
+## License
+
+This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License version 3 as published by the Free Software Foundation.
+
+This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.