From f7acb14822f1a962a211c0d11488ffceadde2b68 Mon Sep 17 00:00:00 2001

From: Pino Toscano <ptoscano@redhat.com>

Date: Fri, 22 Mar 2019 12:59:11 +0100

Subject: [PATCH] common/mltools: allow fd for machine readable output

Allow to specify a file descriptor for the machine readable output.

Use the same assumption as done in v2v, i.e. that Unix.file_descr is

simply the int file descriptor.

(cherry picked from commit 70514dfaf1e45b5ad34f20f3297af9782099cf80)

---

 common/mltools/test-machine-readable.sh |  7 +++++++

 common/mltools/tools_utils.ml           | 11 ++++++++++-

 lib/guestfs.pod                         |  5 +++++

 3 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/common/mltools/test-machine-readable.sh b/common/mltools/test-machine-readable.sh

index 1162c58e9..824460e6d 100755

--- a/common/mltools/test-machine-readable.sh

+++ b/common/mltools/test-machine-readable.sh

@@ -65,3 +65,10 @@ test $($t --machine-readable=stream:stdout |& wc -l) -eq 3

 # Output "stream:stderr".

 $t --machine-readable=stream:stderr 2>&1 >/dev/null | grep 'machine-readable'

 test $($t --machine-readable=stream:stderr 2>&1 >/dev/null | wc -l) -eq 2

+

+# Output "fd:".

+fn="$tmpdir/fdfile"

+exec 4>"$fn"

+$t --machine-readable=fd:4

+exec 4>&-

+test $(cat "$fn" | wc -l) -eq 1

diff --git a/common/mltools/tools_utils.ml b/common/mltools/tools_utils.ml

index ade4cb37f..35478f39e 100644

--- a/common/mltools/tools_utils.ml

+++ b/common/mltools/tools_utils.ml

@@ -41,6 +41,7 @@ type machine_readable_output_type =

   | NoOutput

   | Channel of out_channel

   | File of string

+  | Fd of int

 let machine_readable_output = ref NoOutput

 let machine_readable_channel = ref None

 let machine_readable () =

@@ -50,7 +51,10 @@ let machine_readable () =

         match !machine_readable_output with

         | NoOutput -> None

         | Channel chan -> Some chan

-        | File f -> Some (open_out f) in

+        | File f -> Some (open_out f)

+        | Fd fd ->

+          (* Note that Unix.file_descr is really just an int. *)

+          Some (Unix.out_channel_of_descr (Obj.magic fd)) in

       machine_readable_channel := chan

     );

     !machine_readable_channel

@@ -296,6 +300,11 @@ let create_standard_options argspec ?anon_fun ?(key_opts = false) ?(machine_read

           | n ->

             error (f_"invalid output stream for --machine-readable: %s") fmt in

         machine_readable_output := Channel chan

+      | "fd" ->

+        (try

+          machine_readable_output := Fd (int_of_string outname)

+        with Failure _ ->

+          error (f_"invalid output fd for --machine-readable: %s") fmt)

       | n ->

         error (f_"invalid output for --machine-readable: %s") fmt

       )

diff --git a/lib/guestfs.pod b/lib/guestfs.pod

index 53cece2da..f11028466 100644

--- a/lib/guestfs.pod

+++ b/lib/guestfs.pod

@@ -3287,6 +3287,11 @@ The possible values are:

 =over 4

+=item B<fd:>I<fd>

+

+The output goes to the specified I<fd>, which is a file descriptor

+already opened for writing.

+

 =item B<file:>F<filename>

 The output goes to the specified F<filename>.

-- 

2.18.4