Fix 'file(1)' command to work on /dev devices.

[libguestfs.git] / daemon / file.c

diff --git a/daemon/file.c b/daemon/file.c
index 0b8b463..c09de71 100644 (file)
--- a/daemon/file.c
+++ b/daemon/file.c
@@ -314,3 +314,57 @@ do_write_file (const char *path, const char *content, int size)
 
   return 0;
 }
+
+/* This runs the 'file' command. */
+char *
+do_file (const char *path)
+{
+  char *out, *err;
+  int r, len, freeit = 0;
+  char *buf;
+
+  /*NEED_ROOT (NULL); - no: we allow people to run this on /dev devices. */
+  ABS_PATH (path, NULL);
+
+  if (strncmp (path, "/dev/", 5) == 0)
+    buf = (char *) path;
+  else {
+    len = strlen (path) + 9;
+    buf = malloc (len);
+    if (!buf) {
+      reply_with_perror ("malloc");
+      return NULL;
+    }
+    snprintf (buf, len, "/sysroot%s", path);
+    freeit = 1;
+  }
+
+  /* file(1) manpage claims "file returns 0 on success, and non-zero on
+   * error", but this is evidently not true.  It always returns 0, in
+   * every scenario I can think up.  So check the target is readable
+   * first.
+   */
+  if (access (buf, R_OK) == -1) {
+    if (freeit) free (buf);
+    reply_with_perror ("access: %s", path);
+    return NULL;
+  }
+
+  r = command (&out, &err, "file", "-bsL", buf, NULL);
+  if (freeit) free (buf);
+
+  if (r == -1) {
+    free (out);
+    reply_with_error ("file: %s: %s", path, err);
+    free (err);
+    return NULL;
+  }
+  free (err);
+
+  /* We need to remove the trailing \n from output of file(1). */
+  len = strlen (out);
+  if (out[len-1] == '\n')
+    out[len-1] = '\0';
+
+  return out;                  /* caller frees */
+}