* stream.c (open_tail): Fix 2013-12-02 regression:

seek_to_end_p argument being ignored, with the
behavior being no initial seek to the end.

* txr.1: Clarified the behavior of the seek-to-end-p
option.

3 files changed, 28 insertions, 5 deletions

diff --git a/ChangeLog b/ChangeLog
index 2b1d4886..abfb9ae8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,14 @@
 2014-02-18  Kaz Kylheku  <kaz@kylheku.com>
 
+	* stream.c (open_tail): Fix 2013-12-02 regression:
+	seek_to_end_p argument being ignored, with the
+	behavior being no initial seek to the end.
+
+	* txr.1: Clarified the behavior of the seek-to-end-p
+	option.
+
+2014-02-18  Kaz Kylheku  <kaz@kylheku.com>
+
 	* combi.c (rperm_gen_full): Update ptail with return value
 	of list_collect. This is not necessary for correctness, but it spares
 	list_collect from having to search for the tail on each call.
diff --git a/stream.c b/stream.c
index 9dd0b742..5b1b966c 100644
--- a/stream.c
+++ b/stream.c
@@ -2082,14 +2082,21 @@ val open_file(val path, val mode_str)
 
 val open_tail(val path, val mode_str, val seek_end_p)
 {
+  FILE *f = w_fopen(c_str(path), c_str(mode_str));
   struct stdio_handle *h;
   val stream;
   unsigned long state = 0;
 
-  stream = make_tail_stream(0, path);
+  if (f && seek_end_p)
+    if (fseek(f, 0, SEEK_END) < 0)
+      uw_throwf(file_error_s, lit("error seeking to end of ~a: ~a/~s"),
+                path, num(errno), string_utf8(strerror(errno)), nao);
+
+  stream = make_tail_stream(f, path);
   h = (struct stdio_handle *) stream->co.handle;
   h->mode = mode_str;
-  tail_strategy(stream, &state);
+  if (!f)
+    tail_strategy(stream, &state);
   return stream;
 }
 
diff --git a/txr.1 b/txr.1
index a9a6d9ab..518fdc20 100644
--- a/txr.1
+++ b/txr.1
@@ -11628,9 +11628,16 @@ the same conventions as the mode argument of the C language fopen function.
 The mode string determines whether the stream is an input stream
 or output stream. Note that the "b" mode is not supported.
 Whether a stream is text or binary depends on which operations
-are invoked on it. The <seek-to-end-p> argument is a boolean whcih
-determines whether the initial read/write position is at the
-start of the file, or just past the end.
+are invoked on it. 
+
+The <seek-to-end-p> argument is a boolean which determines whether the initial
+read/write position is at the start of the file, or just past the end.  This
+argument only makes a difference if the file exists at the time open-tail is
+called. If the file does not exist, and is later created, then the tail stream
+will follow that file from the beginning.  In other words, <seek-to-end-p>
+controls whether the tail stream reads all the existing data in the file, if
+any, or whether it reads only newly added data from approximately the time the
+stream is created.
 
 A tail stream has special semantics with regard to reading at the end
 of file. A tail stream never reports an end-of-file condition; instead