dd oflag=append of=FOO without conv=notrunc

[Paul Eggert]

I installed this to warn about the possibly-unexpected consequences
of those options:

2006-08-09  Paul Eggert  <address@hidden>

        * doc/coreutils.texi (dd invocation): Warn about oflag=append without
        conv=notrunc.  See Debian bug 373736.
        * src/dd.c (usage): Warn about oflag=append without conv=notrunc.

Index: doc/coreutils.texi
===================================================================
RCS file: /fetish/cu/doc/coreutils.texi,v
retrieving revision 1.344
diff -p -u -r1.344 coreutils.texi
--- doc/coreutils.texi  8 Aug 2006 22:11:49 -0000       1.344
+++ doc/coreutils.texi  9 Aug 2006 21:15:33 -0000
@@ -7302,6 +7302,9 @@ system.
 Write in append mode, so that even if some other process is writing to
 this file, every @command{dd} write will append to the current
 contents of the file.  This flag makes sense only for output.
+If you combine this flag with the @address@hidden operand,
+you should also specify @samp{conv=notrunc} unless you want the
+output file to be truncated before being appended to.
 
 @item direct
 @opindex direct
Index: src/dd.c
===================================================================
RCS file: /fetish/cu/src/dd.c,v
retrieving revision 1.195
diff -p -u -r1.195 dd.c
--- src/dd.c    9 Jul 2006 17:01:38 -0000       1.195
+++ src/dd.c    9 Aug 2006 21:15:33 -0000
@@ -458,7 +458,7 @@ Each CONV symbol may be:\n\
 \n\
 Each FLAG symbol may be:\n\
 \n\
-  append    append mode (makes sense only for output)\n\
+  append    append mode (makes sense only for output; conv=notrunc 
suggested)\n\
 "), stdout);
       if (O_DIRECT)
        fputs (_("  direct    use direct I/O for data\n"), stdout);