diff --git a/ca-store-generator.js b/ca-store-generator.js
index 26a09ea..9f854f4 100644
--- a/ca-store-generator.js
+++ b/ca-store-generator.js
@@ -6,7 +6,6 @@ var fs = require('fs')
   , path = require('path')
   , request = require('request')
   , CERTDB_URL = 'https://mxr.mozilla.org/nss/source/lib/ckfw/builtins/certdata.txt?raw=1'
-  , OUTFILE = path.join(__dirname, './ssl-root-cas-latest.js')
   , HEADER
   ;
 
@@ -112,18 +111,16 @@ function parseCertData(lines) {
   return certs;
 }
 
-function dumpCerts(certs) {
+function dumpCerts(certs, filename, pemsDir) {
   certs.forEach(function (cert, i) {
-    var pathname = path.join(__dirname, 'pems', 'ca-' + i + '.pem')
-      ;
-
-    fs.writeFileSync(pathname, cert.quasiPEM());
+    var pemsFile = path.join(pemsDir, 'ca-' + i + '.pem');
+    fs.writeFileSync(pemsFile, cert.quasiPEM());
   });
   console.info("Wrote " + certs.length + " certificates in '"
     + path.join(__dirname, 'pems/').replace(/'/g, "\\'") + "'.");
 
   fs.writeFileSync(
-    OUTFILE
+    filename
   , HEADER
       + 'var cas = module.exports = [\n'
       + certs.map(function (cert) { return cert.quasiPEM(); }).join(',\n\n')
@@ -145,9 +142,25 @@ function dumpCerts(certs) {
       + "  return module.exports;\n"
       + "};\n"
   );
-  console.info("Wrote '" + OUTFILE.replace(/'/g, "\\'") + "'.");
+  console.info("Wrote '" + filename.replace(/'/g, "\\'") + "'.");
 }
 
+if (process.argv[2] == null) {
+    console.error("Error: No file specified");
+    console.info("Usage: %s <outputfile>", process.argv[1]);
+    console.info("   where <outputfile> is the name of the file to write to, relative to %s", process.argv[1]);
+    console.info("Note that a 'pems/' directory will also be created at the same location as the <outputfile>, containing individual .pem files.");
+    process.exit(3);
+}
+
+// main (combined) output file location, relative to this script's location
+var outputFile = path.resolve(__dirname, process.argv[2]);
+
+// pems/ output directory, in the same directory as the outputFile
+var outputPemsDir = path.resolve(outputFile, '../pems')
+
+
+console.info("Loading latest certificates from " + CERTDB_URL);
 request(CERTDB_URL, function (error, response, body) {
   if (error) {
     console.error(error.stacktrace);
@@ -160,5 +173,5 @@ request(CERTDB_URL, function (error, response, body) {
   }
 
   var lines = body.split("\n");
-  dumpCerts(parseCertData(lines));
+  dumpCerts(parseCertData(lines), outputFile, outputPemsDir);
 });
diff --git a/package.json b/package.json
index 04986d1..a8839e1 100644
--- a/package.json
+++ b/package.json
@@ -4,9 +4,9 @@
   "description": "The module you need to solve node's SSL woes when including a custom certificate.",
   "main": "ssl-root-cas",
   "scripts": {
-    "test": "node ca-store-generator.js",
-    "prepublish": "node ca-store-generator.js; mv ssl-root-cas-latest.js ssl-root-cas.js",
-    "postinstall": "node ca-store-generator.js; mv ssl-root-cas-latest.js latest.js"
+    "test": "node ca-store-generator.js ssl-root-cas-test.js",
+    "prepublish": "node ca-store-generator.js ssl-root-cas.js",
+    "postinstall": "node ca-store-generator.js latest.js"
   },
   "repository": {
     "type": "git",