[gegl] Check return value of system()

[Mukund Sivaraman <muks src gnome org>]

commit 6992a09e34ffc0e4de5290dc90427a1e8e5cec20
Author: Mukund Sivaraman <muks banu com>
Date:   Thu Jul 29 17:44:15 2010 +0530

    Check return value of system()

 gegl/gegl-dot.c                 |    3 ++-
 operations/common/introspect.c  |    3 ++-
 operations/common/magick-load.c |    3 ++-
 3 files changed, 6 insertions(+), 3 deletions(-)
---
diff --git a/gegl/gegl-dot.c b/gegl/gegl-dot.c
index 6d98af4..181e721 100644
--- a/gegl/gegl-dot.c
+++ b/gegl/gegl-dot.c
@@ -346,5 +346,6 @@ gegl_dot_node_to_png (GeglNode    *node,
 
   /* Create a png from it */
   dot_cmd = g_strdup_printf ("dot -o %s -Tpng %s", png_path, dot_filename);
-  system (dot_cmd);
+  if (system (dot_cmd) == -1)
+    g_warning ("Error executing GraphViz dot program");
 }
diff --git a/operations/common/introspect.c b/operations/common/introspect.c
index 7ece8c3..6b67d6b 100644
--- a/operations/common/introspect.c
+++ b/operations/common/introspect.c
@@ -59,7 +59,8 @@ gegl_introspect_load_cache (GeglChantO *op_introspect)
 
   /* Process the .dot to a .png */
   dot_cmd = g_strdup_printf ("dot -o %s -Tpng %s", png_filename, dot_filename);
-  system (dot_cmd);
+  if (system (dot_cmd) == -1)
+    g_warning ("Error executing GraphViz dot program");
 
   /* Create a graph that loads the png into a GeglBuffer and process
    * it
diff --git a/operations/common/magick-load.c b/operations/common/magick-load.c
index c6ae9aa..c0144a3 100644
--- a/operations/common/magick-load.c
+++ b/operations/common/magick-load.c
@@ -50,7 +50,8 @@ load_cache (GeglChantO *op_magick_load)
       filename = g_build_filename (g_get_tmp_dir (), "gegl-magick.png", NULL);
       cmd = g_strdup_printf ("convert \"%s\"'[0]' \"%s\"",
                              op_magick_load->path, filename);
-      system (cmd);
+      if (system (cmd) == -1)
+        g_warning ("Error executing ImageMagick convert program");
 
       graph = gegl_graph (sink=gegl_node ("gegl:buffer-sink", "buffer", &newbuf, NULL,
                                           gegl_node ("gegl:png-load", "path", filename, NULL)));