update readme

README.md

@@ -1,3 +1,40 @@
 # Sub-Resource Integrity Generator Scripts
 
-Basic scripts to generate SRI hashs for a given file. POSIX-compliant shell script for use on *nix and PowerShell for use on Windows.
+Basic scripts to generate SRI hashes for a given file. POSIX-compliant shell script for use on *nix and PowerShell for use on Windows.
+
+## linux script
+
+- This script *requires* openssl be installed and will exit if it cannot find openssl.
+- You can rename *sri* to anything you like.
+- I suggest copying *sri* somewhere like */usr/local/bin* or */usr/bin* so it can be run easier and from anywhere
+- Complete help is included in the script. Simply run without any parameters or run with '*--help*'
+
+### examples
+
+Assuming you have *not* copied the script to your path and it is located in your home directory:
+
+```bash
+cd ~
+./sri -f /var/www/css/style.css
+```
+
+If copied to a directory in your path like */usr/local/bin*, then you can simplify things by running it directly from where the file you want to hash is located:
+
+```bash
+cd /var/www/css
+sri -f style.css
+```
+
+### troubleshooting
+
+About the only thing that can go wrong is the script not being marked executable. In that case, simply make it executable:
+
+```bash
+# make executable
+chmod +x /path/to/sri
+# verify
+ls -lA /path/to/sri
+# output something like:
+# -rwxr-xr-x 1 user user 3622 Jun 20 01:18 sri
+# note the x's --> -rwXr-Xr-X (capitals for emphasis)
+```