resize: Add --machine-readable option for machine friendly output.

Use virt-resize --machine-readable to print a list of facts about what
this version of virt-resize supports.

This includes parts of commit 09a7545649e6cac0de2c4421cb64b659164174ee
from the development branch, but doesn't include the machine-readable
progress bar.

diff --git a/resize/resize.ml b/resize/resize.ml
index d4455eb..8ee6faa 100644 (file)
--- a/resize/resize.ml
+++ b/resize/resize.ml
@@ -57,6 +57,7 @@ let infile, outfile, copy_boot_loader, debug, deletes, dryrun,
   let format = ref "" in
   let ignores = ref [] in
   let lv_expands = ref [] in
+  let machine_readable = ref false in
   let ntfsresize_force = ref false in
   let output_format = ref "" in
   let quiet = ref false in
@@ -83,6 +84,7 @@ let infile, outfile, copy_boot_loader, debug, deletes, dryrun,
     "--LV-expand", Arg.String (add lv_expands), "lv -\"-";
     "--lvexpand", Arg.String (add lv_expands), "lv -\"-";
     "--LVexpand", Arg.String (add lv_expands), "lv -\"-";
+    "--machine-readable", Arg.Set machine_readable, " Make output machine readable";
     "-n",        Arg.Set dryrun,            " Don't perform changes";
     "--dryrun",  Arg.Set dryrun,            " -\"-";
     "--dry-run", Arg.Set dryrun,            " -\"-";
@@ -125,6 +127,7 @@ read the man page virt-resize(1).
   let format = match !format with "" -> None | str -> Some str in
   let ignores = List.rev !ignores in
   let lv_expands = List.rev !lv_expands in
+  let machine_readable = !machine_readable in
   let ntfsresize_force = !ntfsresize_force in
   let output_format = match !output_format with "" -> None | str -> Some str in
   let quiet = !quiet in
@@ -132,6 +135,25 @@ read the man page virt-resize(1).
   let resizes_force = List.rev !resizes_force in
   let shrink = match !shrink with "" -> None | str -> Some str in
 
+  (* No arguments and machine-readable mode?  Print out some facts
+   * about what this binary supports.  We only need to print out new
+   * things added since this option, or things which depend on features
+   * of the appliance.
+   *)
+  if !disks = [] && machine_readable then (
+    printf "virt-resize\n";
+    printf "ntfsresize-force\n";
+    printf "32bitok\n";
+    let g = new G.guestfs () in
+    g#add_drive_opts "/dev/null";
+    g#launch ();
+    if feature_available g [| "ntfsprogs"; "ntfs3g" |] then
+      printf "ntfs\n";
+    if feature_available g [| "btrfs" |] then
+      printf "btrfs\n";
+    exit 0
+  );
+
   (* Verify we got exactly 2 disks. *)
   let infile, outfile =
     match List.rev !disks with

diff --git a/resize/virt-resize.pod b/resize/virt-resize.pod
index 3a6af18..72b4620 100644 (file)
--- a/resize/virt-resize.pod
+++ b/resize/virt-resize.pod
@@ -349,6 +349,12 @@ You can give this option multiple times, I<but> it doesn't
 make sense to do this unless the logical volumes you specify
 are all in different volume groups.
 
+=item B<--machine-readable>
+
+This option is used to make the output more machine friendly
+when being parsed by other programs.  See
+L</MACHINE READABLE OUTPUT> below.
+
 =item B<-n>
 
 =item B<--dryrun>
@@ -483,6 +489,25 @@ Display version number and exit.
 
 =back
 
+=head1 MACHINE READABLE OUTPUT
+
+The I<--machine-readable> option can be used to make the output more
+machine friendly, which is useful when calling virt-resize from other
+programs, GUIs etc.
+
+Use the option on its own to query the capabilities of the virt-resize
+binary.  Typical output looks like this:
+
+ $ virt-resize --machine-readable
+ virt-resize
+ ntfsresize-force
+ 32bitok
+ ntfs
+ btrfs
+
+A list of features is printed, one per line, and the program exits
+with status 0.
+
 =head1 NOTES
 
 =head2 "Partition 1 does not end on cylinder boundary."