Add command trace functionality.

Enable this by calling guestfs_trace (handle, 1) or by
setting the LIBGUESTFS_TRACE=1 environment variable.

4 files changed, 100 insertions, 0 deletions

diff --git a/guestfish.pod b/guestfish.pod
index 2e50873f..d24c1628 100644
--- a/guestfish.pod
+++ b/guestfish.pod
@@ -568,6 +568,10 @@ Set the default qemu binary that libguestfs uses.  If not set, then
 the qemu which was found at compile time by the configure script is
 used.
 
+=item LIBGUESTFS_TRACE
+
+Set C<LIBGUESTFS_TRACE=1> to enable command traces.
+
 =item PAGER
 
 The C<more> command uses C<$PAGER> as the pager.  If not
diff --git a/guestfs.pod b/guestfs.pod
index d8e4da3b..b8379d04 100644
--- a/guestfs.pod
+++ b/guestfs.pod
@@ -983,6 +983,11 @@ used.
 
 See also L</QEMU WRAPPERS> above.
 
+=item LIBGUESTFS_TRACE
+
+Set C<LIBGUESTFS_TRACE=1> to enable command traces.  This
+has the same effect as calling C<guestfs_set_trace (handle, 1)>.
+
 =item TMPDIR
 
 Location of temporary directory, defaults to C</tmp>.
diff --git a/src/generator.ml b/src/generator.ml
index b0f95436..71aeeed8 100755
--- a/src/generator.ml
+++ b/src/generator.ml
@@ -805,6 +805,32 @@ is passed to the appliance at boot time.  See C<guestfs_set_selinux>.
 For more information on the architecture of libguestfs,
 see L<guestfs(3)>.");
 
+  ("set_trace", (RErr, [Bool "trace"]), -1, [FishAlias "trace"],
+   [InitNone, Always, TestOutputTrue (
+      [["set_trace"; "true"];
+       ["get_trace"]])],
+   "enable or disable command traces",
+   "\
+If the command trace flag is set to 1, then commands are
+printed on stdout before they are executed in a format
+which is very similar to the one used by guestfish.  In
+other words, you can run a program with this enabled, and
+you will get out a script which you can feed to guestfish
+to perform the same set of actions.
+
+If you want to trace C API calls into libguestfs (and
+other libraries) then possibly a better way is to use
+the external ltrace(1) command.
+
+Command traces are disabled unless the environment variable
+C<LIBGUESTFS_TRACE> is defined and set to C<1>.");
+
+  ("get_trace", (RBool "trace", []), -1, [],
+   [],
+   "get command trace enabled flag",
+   "\
+Return the command trace flag.");
+
 ]
 
 (* daemon_functions are any functions which cause some action
@@ -4643,6 +4669,52 @@ check_state (guestfs_h *g, const char *caller)
 
 ";
 
+  (* Generate code to generate guestfish call traces. *)
+  let trace_call shortname style =
+    pr "  if (guestfs__get_trace (g)) {\n";
+
+    let needs_i =
+      List.exists (function
+		   | StringList _ | DeviceList _ -> true
+		   | _ -> false) (snd style) in
+    if needs_i then (
+      pr "    int i;\n";
+      pr "\n"
+    );
+
+    pr "    printf (\"%s\");\n" shortname;
+    List.iter (
+      function
+      | String n			(* strings *)
+      | Device n
+      | Pathname n
+      | Dev_or_Path n
+      | FileIn n
+      | FileOut n ->
+	  (* guestfish doesn't support string escaping, so neither do we *)
+	  pr "    printf (\" \\\"%%s\\\"\", %s);\n" n
+      | OptString n ->			(* string option *)
+	  pr "    if (%s) printf (\" \\\"%%s\\\"\", %s);\n" n n;
+	  pr "    else printf (\" null\");\n"
+      | StringList n
+      | DeviceList n ->			(* string list *)
+	  pr "    putchar (' ');\n";
+	  pr "    putchar ('\"');\n";
+	  pr "    for (i = 0; %s[i]; ++i) {\n" n;
+	  pr "      if (i > 0) putchar (' ');\n";
+	  pr "      fputs (%s[i], stdout);\n" n;
+	  pr "    }\n";
+	  pr "    putchar ('\"');\n";
+      | Bool n ->			(* boolean *)
+	  pr "    fputs (%s ? \" true\" : \" false\", stdout);\n" n
+      | Int n ->			(* int *)
+	  pr "    printf (\" %%d\", %s);\n" n
+    ) (snd style);
+    pr "    putchar ('\\n');\n";
+    pr "  }\n";
+    pr "\n";
+  in
+
   (* For non-daemon functions, generate a wrapper around each function. *)
   List.iter (
     fun (shortname, style, _, _, _, _, _) ->
@@ -4651,6 +4723,7 @@ check_state (guestfs_h *g, const char *caller)
       generate_prototype ~extern:false ~semicolon:false ~newline:true
         ~handle:"g" name style;
       pr "{\n";
+      trace_call shortname style;
       pr "  return guestfs__%s " shortname;
       generate_c_call_args ~handle:"g" style;
       pr ";\n";
@@ -4758,6 +4831,7 @@ check_state (guestfs_h *g, const char *caller)
       pr "  guestfs_main_loop *ml = guestfs_get_main_loop (g);\n";
       pr "  int serial;\n";
       pr "\n";
+      trace_call shortname style;
       pr "  if (check_state (g, \"%s\") == -1) return %s;\n" name error_code;
       pr "  guestfs_set_busy (g);\n";
       pr "\n";
diff --git a/src/guestfs.c b/src/guestfs.c
index 571205f2..98d99b84 100644
--- a/src/guestfs.c
+++ b/src/guestfs.c
@@ -170,6 +170,7 @@ struct guestfs_h
   int cmdline_size;
 
   int verbose;
+  int trace;
   int autosync;
 
   char *path;			/* Path to kernel, initrd. */
@@ -238,6 +239,9 @@ guestfs_create (void)
   str = getenv ("LIBGUESTFS_DEBUG");
   g->verbose = str != NULL && strcmp (str, "1") == 0;
 
+  str = getenv ("LIBGUESTFS_TRACE");
+  g->trace = str != NULL && strcmp (str, "1") == 0;
+
   str = getenv ("LIBGUESTFS_PATH");
   g->path = str != NULL ? strdup (str) : strdup (GUESTFS_DEFAULT_PATH);
   if (!g->path) goto error;
@@ -734,6 +738,19 @@ guestfs__version (guestfs_h *g)
   return r;
 }
 
+int
+guestfs__set_trace (guestfs_h *g, int t)
+{
+  g->trace = !!t;
+  return 0;
+}
+
+int
+guestfs__get_trace (guestfs_h *g)
+{
+  return g->trace;
+}
+
 /* Add a string to the current command line. */
 static void
 incr_cmdline_size (guestfs_h *g)