[PATCH] stdbuf: make it mandatory to specify a buffering option

[Pádraig Brady]

This is consistent with the documented interface and
avoids any ambiguity in a user thinking that stdbuf without options
might reset to a "standard" buffering setup.

* src/stdbuf.c (set_libstdbuf_options): Indicate with the return value
whether any env variables were actually set.
(main): Fail unless some env variables were set.
* tests/misc/stdbuf.sh: Ensure this constraint is enforced.
---
 src/stdbuf.c         |   17 +++++++++++------
 tests/misc/stdbuf.sh |    2 ++
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/src/stdbuf.c b/src/stdbuf.c
index 38e9bee..a7eb0a0 100644
--- a/src/stdbuf.c
+++ b/src/stdbuf.c
@@ -248,12 +248,14 @@ set_LD_PRELOAD (void)
     }
 }
 
-/* Populate environ with _STDBUF_I=$MODE _STDBUF_O=$MODE _STDBUF_E=$MODE  */
+/* Populate environ with _STDBUF_I=$MODE _STDBUF_O=$MODE _STDBUF_E=$MODE.
+   Return TRUE if any environment variables set.   */
 
-static void
+static bool
 set_libstdbuf_options (void)
 {
-  unsigned int i;
+  bool env_set = false;
+  size_t i;
 
   for (i = 0; i < ARRAY_CARDINALITY (stdbuf); i++)
     {
@@ -278,8 +280,12 @@ set_libstdbuf_options (void)
                      _("failed to update the environment with %s"),
                      quote (var));
             }
+
+          env_set = true;
         }
     }
+
+  return env_set;
 }
 
 int
@@ -346,9 +352,8 @@ main (int argc, char **argv)
       usage (EXIT_CANCELED);
     }
 
-  /* FIXME: Should we mandate at least one option?  */
-
-  set_libstdbuf_options ();
+  if (! set_libstdbuf_options ())
+      error (EXIT_CANCELED, 0, _("you must specify a buffering mode option"));
 
   /* Try to preload libstdbuf first from the same path as
      stdbuf is running from.  */
diff --git a/tests/misc/stdbuf.sh b/tests/misc/stdbuf.sh
index 12347ec..650e8e7 100755
--- a/tests/misc/stdbuf.sh
+++ b/tests/misc/stdbuf.sh
@@ -50,6 +50,8 @@ stdbuf -o$SIZE_OFLOW true # size too large
 test $? = 125 || fail=1
 stdbuf -iL true # line buffering stdin disallowed
 test $? = 125 || fail=1
+stdbuf true # a buffering mode must be specified
+test $? = 125 || fail=1
 stdbuf -i0 -o0 -e0 true || fail=1 #check all files
 stdbuf -o1 . # invalid command
 test $? = 126 || fail=1
-- 
1.7.7.6