Index: ChangeLog
===================================================================
RCS file: /cvsroot/tcl/tcl/ChangeLog,v
retrieving revision 1.1453.2.609
diff -w -u -r1.1453.2.609 ChangeLog
--- ChangeLog	16 Mar 2006 00:35:53 -0000	1.1453.2.609
+++ ChangeLog	16 Mar 2006 18:15:22 -0000
@@ -1,3 +1,13 @@
+2006-03-16  Andreas Kupries <andreask@activestate.com>
+
+	* generic/tclIOUtil.c (TclGetOpenMode): Added the flag O_APPEND to
+	  the list of POSIX modes used when opening a file for
+	  'a'ppend. This enables the proper automatic seek-to-end-on-write
+	  by the OS. See [Bug 680143] for longer discussion.
+
+	* tests/ioCmd.test (iocmd-13.7.*): Extended the testsuite to check
+	  the new handling of 'a'.
+
 2006-03-15  Andreas Kupries <andreask@activestate.com>
 
 	* tests/socket.test: Extended the timeout in socket-11.11 from 10
Index: generic/tclIOUtil.c
===================================================================
RCS file: /cvsroot/tcl/tcl/generic/tclIOUtil.c,v
retrieving revision 1.77.2.26
diff -w -u -r1.77.2.26 tclIOUtil.c
--- generic/tclIOUtil.c	15 Feb 2006 16:04:29 -0000	1.77.2.26
+++ generic/tclIOUtil.c	16 Mar 2006 18:15:22 -0000
@@ -1567,7 +1567,11 @@
 		mode = O_WRONLY|O_CREAT|O_TRUNC;
 		break;
 	    case 'a':
-		mode = O_WRONLY|O_CREAT;
+	        /* [Bug 680143].
+		 * Added O_APPEND for proper automatic
+		 * seek-to-end-on-write by the OS.
+		 */
+	        mode = O_WRONLY|O_CREAT|O_APPEND;
                 *seekFlagPtr = 1;
 		break;
 	    default:
Index: tests/ioCmd.test
===================================================================
RCS file: /cvsroot/tcl/tcl/tests/ioCmd.test,v
retrieving revision 1.16.2.2
diff -w -u -r1.16.2.2 ioCmd.test
--- tests/ioCmd.test	7 Oct 2003 18:53:23 -0000	1.16.2.2
+++ tests/ioCmd.test	16 Mar 2006 18:15:22 -0000
@@ -1,3 +1,4 @@
+# -*- tcl -*-
 # Commands covered: open, close, gets, read, puts, seek, tell, eof, flush,
 #		    fblocked, fconfigure, open, channel, fcopy
 #
@@ -459,6 +460,42 @@
 	string tolower $msg
 } {1 {couldn't open "_non_existent_": no such file or directory} {posix enoent {no such file or directory}}}
 
+
+test iocmd-13.7.1 {open for append, a mode} -setup {
+    set log   [makeFile {} out]
+    set chans {}
+} -body {
+    foreach i { 0 1 2 3 4 5 6 7 8 9 } {
+	puts [set ch [open $log a]] $i
+	lappend chans $ch
+    }
+    foreach ch $chans {catch {close $ch}}
+    lsort [split [string trim [viewFile out]] \n]
+} -cleanup {
+    removeFile out
+    # Ensure that channels are gone, even if body failed to do so
+    foreach ch $chans {catch {close $ch}}
+} -result {0 1 2 3 4 5 6 7 8 9}
+
+test iocmd-13.7.2 {open for append, O_APPEND} -setup {
+    set log   [makeFile {} out]
+    set chans {}
+} -body {
+    foreach i { 0 1 2 3 4 5 6 7 8 9 } {
+	puts [set ch [open $log {WRONLY CREAT APPEND}]] $i
+	lappend chans $ch
+    }
+    foreach ch $chans {catch {close $ch}}
+    lsort [split [string trim [viewFile out]] \n]
+} -cleanup {
+    removeFile out
+    # Ensure that channels are gone, even if body failed to do so
+    foreach ch $chans {catch {close $ch}}
+} -result {0 1 2 3 4 5 6 7 8 9}
+
+
+
+
 test iocmd-14.1 {file id parsing errors} {
     list [catch {eof gorp} msg] $msg $errorCode
 } {1 {can not find channel named "gorp"} NONE}
