Implement nss-altfiles-config tool

Closes issue #4

.gitignore

@@ -1,3 +1,4 @@
+nss-altfiles-config
 *.so*
 *.o
 .*.sw[op]

Makefile

@@ -43,17 +43,20 @@ ifneq ($(strip $(BUILDAPI_JOBS)),)
   MAKEOPTS += -j$(BUILDAPI_JOBS)
 endif
 
-all: $T
+all: $T nss-altfiles-config
 
 $T: $O
 	$(CC) -shared -o $@ $^ $(LDFLAGS)
 
 $O: src/nss_altfiles/files-XXX.c src/nss_altfiles/files-parse.c src/compat.h
 src/nss_altfiles/files-hosts.o: src/resolv/mapv4v6addr.h  src/resolv/res_hconf.h
 
+nss-altfiles-config: src/main.o
+	$(CC) -o $@ $^
+
 clean:
 	find src -name '*.o' -delete
-	$(RM) $T
+	$(RM) $T nss-altfiles-config
 
 distclean: clean
 	$(RM) config.mk

src/main.c

@@ -0,0 +1,36 @@
+/*
+ * main.c
+ * Copyright (C) 2015 Adrian Perez <aperez@igalia.com>
+ *
+ * Distributed under terms of the MIT license.
+ */
+
+#include "compat.h"
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+
+#define XSTRINGIZE(y) #y
+#define STRINGIZE(x)  XSTRINGIZE(x)
+
+static int
+usage (const char *prgname)
+{
+    fprintf (stderr, "Usage: %s [datadir | modulename]\n", prgname);
+    return EXIT_FAILURE;
+}
+
+int
+main (int argc, const char *argv[])
+{
+    if (argc > 2) return usage (argv[0]);
+
+    if (argc == 1 || strcmp (argv[1], "datadir") == 0) {
+        printf ("%s\n", ALTFILES_DATADIR);
+    } else if (strcmp (argv[1], "modulename") == 0) {
+        printf ("%s\n", STRINGIZE (ALTFILES_MODULE_NAME));
+    } else {
+        return usage (argv[0]);
+    }
+    return EXIT_SUCCESS;
+}