From: Jim Meyering <meyering@redhat.com>
Date: Thu, 1 Nov 2007 20:25:28 +0000 (+0100)
Subject: Say that the first process substitution example is contrived.
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X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e556eaa59edf8dfecc763fb13cf288fb1b4d3a40;p=thirdparty%2Fcoreutils.git

Say that the first process substitution example is contrived.

* doc/coreutils.texi (tee invocation): ... and show how to do
it properly.  Pointed out by James Antill.
---

diff --git a/ChangeLog b/ChangeLog
index cfb5c79cba..e39c84e3c1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2007-11-01  Jim Meyering  <meyering@redhat.com>
 
+	Say that the first process substitution example is contrived.
+	* doc/coreutils.texi (tee invocation): ... and show how to do
+	it properly.  Pointed out by James Antill.
+
 	Use mktemp, not mkdtemp, to create test directories.
 	* tests/test-lib.sh: Use the mktemp binary we've just built,
 	not the mkdtemp script.
diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index aa25fcd080..9c960a57e0 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -11076,6 +11076,7 @@ and SHA1 computation.  Then, you'll get the checksum for
 free, because the entire process parallelizes so well:
 
 @example
+# slightly contrived, to demonstrate process substitution
 wget -O - http://example.com/dvd.iso \
   | tee >(sha1sum > dvd.sha1) > dvd.iso
 @end example
@@ -11093,8 +11094,17 @@ so it works with @command{zsh}, @command{bash}, and @command{ksh},
 but not with @command{/bin/sh}.  So if you write code like this
 in a shell script, be sure to start the script with @samp{#!/bin/bash}.
 
+Since the above example writes to one file and one process,
+a more conventional and portable use of @command{tee} is even better:
+
+@example
+wget -O - http://example.com/dvd.iso \
+  | tee dvd.iso | sha1sum > dvd.sha1
+@end example
+
 You can extend this example to make @command{tee} write to two processes,
-computing MD5 and SHA1 checksums in parallel:
+computing MD5 and SHA1 checksums in parallel.  In this case,
+process substitution is required:
 
 @example
 wget -O - http://example.com/dvd.iso \