New APIs: is-zero and is-zero-device, to test if file or device is all zeroes.

[libguestfs.git] / generator / generator_actions.ml

diff --git a/generator/generator_actions.ml b/generator/generator_actions.ml
index 9c5aefd..d0aac87 100644 (file)
--- a/generator/generator_actions.ml
+++ b/generator/generator_actions.ml
@@ -2268,15 +2268,12 @@ The exact command which runs is C<file -zb path>.  Note in
 particular that the filename is not prepended to the output
 (the I<-b> option).
 
-This command can also be used on C</dev/> devices
-(and partitions, LV names).  You can for example use this
-to determine if a device contains a filesystem, although
-it's usually better to use C<guestfs_vfs_type>.
+The output depends on the output of the underlying L<file(1)>
+command and it can change in future in ways beyond our control.
+In other words, the output is not guaranteed by the ABI.
 
-If the C<path> does not begin with C</dev/> then
-this command only works for the content of regular files.
-For other file types (directory, symbolic link etc) it
-will just return the string C<directory> etc.");
+See also: L<file(1)>, C<guestfs_vfs_type>, C<guestfs_lstat>,
+C<guestfs_is_file>, C<guestfs_is_blockdev> (etc), C<guestfs_is_zero>.");
 
   ("command", (RString "output", [StringList "arguments"], []), 50, [ProtocolLimitWarning],
    [InitScratchFS, Always, TestOutput (
@@ -2982,7 +2979,8 @@ How many blocks are zeroed isn't specified (but it's I<not> enough
 to securely wipe the device).  It should be sufficient to remove
 any partition tables, filesystem superblocks and so on.
 
-See also: C<guestfs_zero_device>, C<guestfs_scrub_device>.");
+See also: C<guestfs_zero_device>, C<guestfs_scrub_device>,
+C<guestfs_is_zero_device>");
 
   ("grub_install", (RErr, [Pathname "root"; Device "device"], []), 86, [],
    (* See:
@@ -5940,6 +5938,29 @@ Instead, use the autosync flag (C<guestfs_set_autosync>) to
 control whether or not this operation is performed when the
 handle is closed.");
 
+  ("is_zero", (RBool "zeroflag", [Pathname "path"], []), 283, [],
+   [InitISOFS, Always, TestOutputTrue (
+      [["is_zero"; "/100kallzeroes"]]);
+    InitISOFS, Always, TestOutputFalse (
+      [["is_zero"; "/100kallspaces"]])],
+   "test if a file contains all zero bytes",
+   "\
+This returns true iff the file exists and the file is empty or
+it contains all zero bytes.");
+
+  ("is_zero_device", (RBool "zeroflag", [Device "device"], []), 284, [],
+   [InitBasicFS, Always, TestOutputTrue (
+      [["umount"; "/dev/sda1"];
+       ["zero_device"; "/dev/sda1"];
+       ["is_zero_device"; "/dev/sda1"]]);
+    InitBasicFS, Always, TestOutputFalse (
+      [["is_zero_device"; "/dev/sda1"]])],
+   "test if a device contains all zero bytes",
+   "\
+This returns true iff the device exists and contains all zero bytes.
+
+Note that for large devices this can take a long time to run.");
+
 ]
 
 let all_functions = non_daemon_functions @ daemon_functions