Warn about oflag=append without conv=notrunc.

4 files changed, 12 insertions, 1 deletions

diff --git a/ChangeLog b/ChangeLog
index b61e0207f..f32f5eace 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,8 @@
 2006-08-09  Paul Eggert  <eggert@cs.ucla.edu>
 
+	* src/dd.c (usage): Warn about oflag=append without conv=notrunc.
+	See Debian bug 373736.
+
 	* src/dircolors.hin: Add mlterm, rxvt-unicode; this fixes Debian
 	bug 317503.
 
diff --git a/doc/ChangeLog b/doc/ChangeLog
index 3f0f26a32..6cdf3743f 100644
--- a/doc/ChangeLog
+++ b/doc/ChangeLog
@@ -1,3 +1,8 @@
+2006-08-09  Paul Eggert  <eggert@cs.ucla.edu>
+
+	* coreutils.texi (dd invocation): Warn about oflag=append without
+	conv=notrunc.  See Debian bug 373736.
+
 2006-08-08  Paul Eggert  <eggert@cs.ucla.edu>
 
 	* coreutils.texi (shuf invocation, Random sources): New sections.
diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 5a497614f..bf4d32f37 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -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 @samp{of=@var{file}} 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
diff --git a/src/dd.c b/src/dd.c
index 276ed7472..ff30eda98 100644
--- a/src/dd.c
+++ b/src/dd.c
@@ -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);