From be2dabef95d5638e40c7c74b2bc1a3a4dd64bae3 Mon Sep 17 00:00:00 2001 From: =?utf8?q?P=C3=A1draig=20Brady?= Date: Tue, 8 May 2012 13:18:45 +0100 Subject: [PATCH] doc: clarify dd conv=sparse usage with devices * doc/coreutils.texi (dd invocation): Clarify that NUL blocks are not copied for devices either, and give examples of where it might be useful. --- doc/coreutils.texi | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/doc/coreutils.texi b/doc/coreutils.texi index 61b3c89..767267b 100644 --- a/doc/coreutils.texi +++ b/doc/coreutils.texi @@ -8167,9 +8167,12 @@ On a file system that supports sparse files, this will create sparse output when extending the output file. Be careful when using this option in conjunction with @samp{conv=notrunc} or @samp{oflag=append}. -With @samp{conv=notrunc}, existing data in the output +With @samp{conv=notrunc}, existing data in the output file corresponding to @sc{nul} blocks from the input, will be untouched. With @samp{oflag=append} the seeks performed will be ineffective. +Similarly, when the output is a device rather than a file, +@sc{nul} input blocks are not copied, and therefore this option +is most useful with virtual or pre zeroed devices. @item swab @opindex swab @r{(byte-swapping)} -- 2.7.4