blkid: Detect when value not found and return empty string.

[libguestfs.git] / daemon / blkid.c

diff --git a/daemon/blkid.c b/daemon/blkid.c
index 4e14881..f631061 100644 (file)
--- a/daemon/blkid.c
+++ b/daemon/blkid.c
@@ -27,16 +27,27 @@
 #include "daemon.h"
 #include "actions.h"
 
-char *
-do_vfs_type (const char *device)
+static char *
+get_blkid_tag (const char *device, const char *tag)
 {
   char *out, *err;
   int r;
 
-  r = command (&out, &err,
-               "/sbin/blkid", "-o", "value", "-s", "TYPE", device, NULL);
-  if (r == -1) {
-    reply_with_error ("vfs_type: %s: %s", device, err);
+  /* Kill the cache file, forcing blkid to reread values from the
+   * original filesystems.  In blkid there is a '-p' option which is
+   * supposed to do this, but (a) it doesn't work and (b) that option
+   * is not supported in RHEL 5.
+   */
+  unlink ("/etc/blkid/blkid.tab"); /* Red Hat, Fedora */
+  unlink ("/etc/blkid.tab"); /* Debian */
+
+  r = commandr (&out, &err,
+                "blkid", "-o", "value", "-s", tag, device, NULL);
+  if (r != 0 && r != 2) {
+    if (r >= 0)
+      reply_with_error ("%s: %s (blkid returned %d)", device, err, r);
+    else
+      reply_with_error ("%s: %s", device, err);
     free (out);
     free (err);
     return NULL;
@@ -44,6 +55,14 @@ do_vfs_type (const char *device)
 
   free (err);
 
+  if (r == 2) {                 /* means UUID etc not found */
+    free (out);
+    out = strdup ("");
+    if (out == NULL)
+      reply_with_perror ("strdup");
+    return out;
+  }
+
   /* Trim trailing \n if present. */
   size_t len = strlen (out);
   if (len > 0 && out[len-1] == '\n')
@@ -51,3 +70,21 @@ do_vfs_type (const char *device)
 
   return out;                   /* caller frees */
 }
+
+char *
+do_vfs_type (const char *device)
+{
+  return get_blkid_tag (device, "TYPE");
+}
+
+char *
+do_vfs_label (const char *device)
+{
+  return get_blkid_tag (device, "LABEL");
+}
+
+char *
+do_vfs_uuid (const char *device)
+{
+  return get_blkid_tag (device, "UUID");
+}