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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.
This commit is contained in:
Jim Meyering
2007-11-01 21:25:28 +01:00
parent 636f0e101a
commit e556eaa59e
2 changed files with 15 additions and 1 deletions
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@@ -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.
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@@ -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 \