From f9bf96bfa7c282394792270c2ed6451b370a5bcd Mon Sep 17 00:00:00 2001 From: Pádraig Brady Date: Sat, 15 Dec 2012 03:15:38 +0000 Subject: doc: clarify when dd iflag=fullblock is useful * doc/coreutils.texi (dd invocation): Explain that iflag=fullblock ensures that count= will count blocks rather than reads, and reference that in both the count= and iflag=fullblock descriptions. Suggested by John Reiser. --- doc/coreutils.texi | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/doc/coreutils.texi b/doc/coreutils.texi index 174a8c386..bed355364 100644 --- a/doc/coreutils.texi +++ b/doc/coreutils.texi @@ -8117,6 +8117,11 @@ Copy @var{n} @samp{ibs}-byte blocks from the input file, instead of everything until the end of the file. if @samp{iflag=count_bytes} is specified, @var{n} is interpreted as a byte count rather than a block count. +Note if the input may return short reads as could be the case +when reading from a pipe for example, @samp{iflag=fullblock} +will ensure that @samp{count=} corresponds to complete input blocks +rather than the traditional POSIX specified behavior of counting +input read operations. @item status=@var{which} @opindex status @@ -8397,6 +8402,10 @@ may return early if a full block is not available. When that happens, continue calling @code{read} to fill the remainder of the block. This flag can be used only with @code{iflag}. +This flag is useful with pipes for example +as they may return short reads. In that case, +this flag is needed to ensure that a @samp{count=} argument is +interpreted as a block count rather than a count of read operations. @item count_bytes @opindex count_bytes -- cgit v1.2.3-54-g00ecf