[PATCH 1/2] tee: exit early if no more writable outputs

[Pádraig Brady]

* src/tee.c (main): Don't continue reading if we can't
output anywhere.
* tests/misc/tee.sh: Ensure we exit when no more outputs.
* NEWS: Mention the change in behavior.
---
 NEWS              |  2 ++
 src/tee.c         | 13 ++++++++++++-
 tests/misc/tee.sh |  9 +++++++++
 3 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/NEWS b/NEWS
index 5bc942c..b6795aa 100644
--- a/NEWS
+++ b/NEWS
@@ -71,6 +71,8 @@ GNU coreutils NEWS                                    -*- 
outline -*-
   insensitive file systems like HFS, mv would just remove a hardlinked 'file'
   if called like `mv file File`.  The feature was added in coreutils-5.0.1.
 
+  tee will exit early if there are no more writable outputs.
+
 ** Improvements
 
   cp,install,mv will convert smaller runs of NULs in the input to holes,
diff --git a/src/tee.c b/src/tee.c
index 04b7ec3..bfe1b69 100644
--- a/src/tee.c
+++ b/src/tee.c
@@ -135,6 +135,7 @@ main (int argc, char **argv)
 static bool
 tee_files (int nfiles, const char **files)
 {
+  size_t n_outputs = 0;
   FILE **descriptors;
   char buffer[BUFSIZ];
   ssize_t bytes_read;
@@ -164,6 +165,7 @@ tee_files (int nfiles, const char **files)
   descriptors[0] = stdout;
   files[0] = _("standard output");
   setvbuf (stdout, NULL, _IONBF, 0);
+  n_outputs++;
 
   for (i = 1; i <= nfiles; i++)
     {
@@ -176,7 +178,10 @@ tee_files (int nfiles, const char **files)
           ok = false;
         }
       else
-        setvbuf (descriptors[i], NULL, _IONBF, 0);
+        {
+          setvbuf (descriptors[i], NULL, _IONBF, 0);
+          n_outputs++;
+        }
     }
 
   while (1)
@@ -194,9 +199,15 @@ tee_files (int nfiles, const char **files)
             && fwrite (buffer, bytes_read, 1, descriptors[i]) != 1)
           {
             error (0, errno, "%s", files[i]);
+            if (descriptors[i] == stdout)
+              clearerr (stdout); /* Avoid redundant close_stdout diagnostic.  
*/
             descriptors[i] = NULL;
             ok = false;
+            n_outputs--;
           }
+
+      if (n_outputs == 0)
+        break;
     }
 
   if (bytes_read == -1)
diff --git a/tests/misc/tee.sh b/tests/misc/tee.sh
index 3c3fd11..1043bec 100755
--- a/tests/misc/tee.sh
+++ b/tests/misc/tee.sh
@@ -31,4 +31,13 @@ for n in 0 $nums; do
         done
 done
 
+
+# Ensure tee exits early if no more writable outputs
+if test -w /dev/full && test -c /dev/full; then
+  yes | returns_ 1 timeout 10 tee /dev/full 2>err >/dev/full || fail=1
+  # Ensure an error for each of the 2 outputs
+  # (and no redundant errors for stdout).
+  test $(wc -l < err) = 2 || { cat err; fail=1; }
+fi
+
 Exit $fail
-- 
2.1.0