diff --git a/src/comp/driver/rustc.rs b/src/comp/driver/rustc.rs
index 69030f3c808..67c26f9b07d 100644
--- a/src/comp/driver/rustc.rs
+++ b/src/comp/driver/rustc.rs
@@ -5,23 +5,111 @@ import front.token;
 import middle.trans;
 import middle.resolve;
 
-io fn main(vec[str] args) {
+import std.util.option;
+import std.util.some;
+import std.util.none;
+import std._str;
+import std._vec;
 
+io fn compile_input(session.session sess, str input, str output) {
+          auto p = parser.new_parser(sess, 0, input);
+          auto crate = parser.parse_crate(p);
+          crate = resolve.resolve_crate(sess, crate);
+          trans.trans_crate(sess, crate, output);
+}
+
+fn warn_wrong_compiler() {
   log "This is the rust 'self-hosted' compiler.";
   log "The one written in rust.";
   log "It does nothing yet, it's a placeholder.";
   log "You want rustboot, the compiler next door.";
+}
+
+fn usage(session.session sess, str argv0) {
+    log #fmt("usage: %s [options] <input>", argv0);
+    log "options:";
+    log "";
+    log "    -o <filename>      write output to <filename>";
+    log "    -nowarn            suppress wrong-compiler warning";
+    log "    -h                 display this message";
+    log "";
+    log "";
+}
+
+io fn main(vec[str] args) {
 
-  auto i = 0;
   auto sess = session.session();
-  for (str filename in args) {
-      if (i > 0) {
-          auto p = parser.new_parser(sess, 0, filename);
-          auto crate = parser.parse_crate(p);
-          crate = resolve.resolve_crate(sess, crate);
-          trans.trans_crate(sess, crate);
+  let option[str] input_file = none[str];
+  let option[str] output_file = none[str];
+  let bool do_warn = true;
+
+  auto i = 1u;
+  auto len = _vec.len[str](args);
+
+  // FIXME: a getopt module would be nice.
+  while (i < len) {
+      auto arg = args.(i);
+      if (_str.byte_len(arg) > 0u && arg.(0) == '-' as u8) {
+          if (_str.eq(arg, "-nowarn")) {
+              do_warn = false;
+          } else {
+              // FIXME: rust could use an elif construct.
+              if (_str.eq(arg, "-o")) {
+                  if (i+1u < len) {
+                      output_file = some(args.(i+1u));
+                      i += 1u;
+                  } else {
+                      usage(sess, args.(0));
+                      sess.err("-o requires an argument");
+                  }
+              } else {
+                  if (_str.eq(arg, "-h")) {
+                      usage(sess, args.(0));
+                  } else {
+                      usage(sess, args.(0));
+                      sess.err("unrecognized option: " + arg);
+                  }
+              }
+          }
+      } else {
+          alt (input_file) {
+              case (some[str](_)) {
+                  usage(sess, args.(0));
+                  sess.err("multiple inputs provided");
+              }
+              case (none[str]) {
+                  input_file = some[str](arg);
+              }
+          }
+          // FIXME: dummy node to work around typestate mis-wiring bug.
+          i = i;
+      }
+      i += 1u;
+  }
+
+  if (do_warn) {
+      warn_wrong_compiler();
+  }
+
+  alt (input_file) {
+      case (none[str]) {
+          usage(sess, args.(0));
+          sess.err("no input filename");
+      }
+      case (some[str](?ifile)) {
+          alt (output_file) {
+              case (none[str]) {
+                  let vec[str] parts = _str.split(ifile, '.' as u8);
+                  parts = _vec.pop[str](parts);
+                  parts += ".bc";
+                  auto ofile = _str.concat(parts);
+                  compile_input(sess, ifile, ofile);
+              }
+              case (some[str](?ofile)) {
+                  compile_input(sess, ifile, ofile);
+              }
+          }
       }
-      i += 1;
   }
 }
 
diff --git a/src/comp/middle/trans.rs b/src/comp/middle/trans.rs
index 6263c3db8cb..83e744ea4d2 100644
--- a/src/comp/middle/trans.rs
+++ b/src/comp/middle/trans.rs
@@ -1095,7 +1095,7 @@ fn trans_main_fn(@trans_ctxt cx, ValueRef llcrate) {
 
 }
 
-fn trans_crate(session.session sess, @ast.crate crate) {
+fn trans_crate(session.session sess, @ast.crate crate, str output) {
     auto llmod =
         llvm.LLVMModuleCreateWithNameInContext(_str.buf("rust_out"),
                                                llvm.LLVMGetGlobalContext());
@@ -1138,7 +1138,7 @@ fn trans_crate(session.session sess, @ast.crate crate) {
     trans_exit_task_glue(cx);
     trans_main_fn(cx, crate_constant(cx));
 
-    llvm.LLVMWriteBitcodeToFile(llmod, _str.buf("rust_out.bc"));
+    llvm.LLVMWriteBitcodeToFile(llmod, _str.buf(output));
     llvm.LLVMDisposeModule(llmod);
 }