From f3d4a2c72f315fd3bb0a939f6331ee0465fcfe2f Mon Sep 17 00:00:00 2001
From: Rob Landley <rob@landley.net>
Date: Sun, 22 Dec 2019 20:54:03 -0600
Subject: Bugfix: tee with no arguments was writing to stdout twice. Add basic
 smoketest while we're at it.

---
 tests/tee.test   |  9 +++++++++
 toys/posix/tee.c | 10 +++++-----
 2 files changed, 14 insertions(+), 5 deletions(-)
 create mode 100755 tests/tee.test

diff --git a/tests/tee.test b/tests/tee.test
new file mode 100755
index 00000000..fd3b9447
--- /dev/null
+++ b/tests/tee.test
@@ -0,0 +1,9 @@
+#!/bin/bash
+
+[ -f testing.sh ] && . testing.sh
+
+#testing "name" "command" "result" "infile" "stdin"
+
+testing "" "tee" "one" "" "one"
+testing "" "tee -" "two\n" "" "two\n"
+testing "" "tee one > two && cmp one two && echo that" "that\n" "" "three"
diff --git a/toys/posix/tee.c b/toys/posix/tee.c
index 78139a8d..ff8a29dc 100644
--- a/toys/posix/tee.c
+++ b/toys/posix/tee.c
@@ -54,18 +54,18 @@ void tee_main(void)
 
   for (;;) {
     struct fd_list *fdl;
-    int len;
+    int len, out = 0;
 
     // Read data from stdin
     len = xread(0, toybuf, sizeof(toybuf));
     if (len<1) break;
 
     // Write data to each output file, plus stdout.
-    fdl = TT.outputs;
-    for (;;) {
-      if(len != writeall(fdl ? fdl->fd : 1, toybuf, len)) toys.exitval=1;
+    for (fdl = TT.outputs; ;fdl = fdl->next) {
+      if (!fdl && out) break;
+      if (len != writeall(fdl ? fdl->fd : 1, toybuf, len)) toys.exitval=1;
       if (!fdl) break;
-      fdl = fdl->next;
+      if (fdl->fd == 1) out++;
     }
   }
 }
-- 
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