diff --git a/shared/replay.go b/shared/replay.go
new file mode 100644
index 0000000..0c835d1
--- /dev/null
+++ b/shared/replay.go
@@ -0,0 +1,117 @@
+package shared
+
+import (
+	"bufio"
+	"os"
+)
+
+const (
+	recording_env_var = "GLLVM_REPLAY_LOG"
+)
+
+/*
+ * Assumming GLLVM_REPLAY_LOG is set, this records the compiler call out to the file indicated by the
+ * value of said environment variable. The format of the record is:
+ *  <start of format>
+ *  pwd
+ *  compiler
+ *  args[0]
+ *  args[1]
+ *  ...
+ *  args[N]
+ *
+ * </start of format>
+ * The end being signalled by a blank line. This format make replaying somewaht trivial.
+ */
+func Record(args []string, compiler string) {
+	logfile := os.Getenv(recording_env_var)
+	if len(logfile) > 0 {
+		fp, err := os.OpenFile(logfile, os.O_WRONLY | os.O_APPEND | os.O_CREATE, os.ModePerm)
+		if err != nil { panic(err) }
+		defer fp.Close()
+		dir, err := os.Getwd()
+		if err != nil { panic(err) }
+		fp.WriteString(dir)
+		fp.WriteString("\n")
+		fp.WriteString(compiler)
+		fp.WriteString("\n")
+		for _, arg := range args {
+			fp.WriteString(arg)
+			fp.WriteString("\n")
+		}
+		fp.WriteString("\n")
+	}
+}
+
+
+type CompilerCall struct {
+	Pwd string
+	Name string
+	Args []string
+}
+
+
+func readCompilerCall(scanner *bufio.Scanner) (call *CompilerCall) {
+	if scanner.Scan() {
+		//got one line, probably an entire call too ...
+		callp := new(CompilerCall)  //pass in a local version later, save on mallocing.
+		line := scanner.Text()
+		if len(line) == 0 {
+			panic("empty CompilerCall.Pwd")
+		}
+		call.Pwd = line
+		if !scanner.Scan() {
+			panic("non-existant CompilerCall.Name")
+		}
+		line = scanner.Text()
+		if len(line) == 0 {
+			panic("empty CompilerCall.Name")
+		}
+		call.Name = line
+
+		for scanner.Scan() {
+			line = scanner.Text()
+			if len(line) == 0 {
+				if len(call.Args) == 0 {
+					panic("empty CompilerCall.Args")
+				}
+				break
+			}
+			call.Args = append(call.Args, line)
+		}
+		call = callp
+	}
+	return
+}
+
+
+/*
+ *
+ */
+func Replay(path string) (ok bool) {
+	fp, err := os.OpenFile(path, os.O_RDONLY, os.ModePerm)
+	if err != nil { return }
+    defer fp.Close()
+	scanner := bufio.NewScanner(fp)
+	for {
+		callp := readCompilerCall(scanner)
+		if callp == nil { return }
+		ok = replayCall(callp)
+		if !ok { return }
+	}
+	ok = true
+	return
+}
+
+/*
+ *
+ */
+func replayCall(call *CompilerCall) bool {
+	err := os.Chdir(call.Pwd)
+	if err != nil { panic(err) }
+	exitCode := Compile(call.Args, call.Name)
+	if exitCode != 0 {
+		return false
+	}
+	return true
+}