doc: give a tee example for combining process substitution outputs

This can be useful if you want to further process data
from process substitutions. For example:
  datagen | tee >(md5sum --tag) > >(sha256sum --tag) | sort

* doc/coreutils.texi (tee invocation): Mention that -p is
useful with pipes that may not consume all data.
Add an example, similar to the one above.
* THANKS.in: Add Jirka Hladky.

1 files changed, 16 insertions, 0 deletions

diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 8034807a4..0e28f4971 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -13019,6 +13019,11 @@ 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}.
 
+Note also that if any of the process substitutions (or piped stdout)
+might exit early without consuming all the data, the @option{-p} option
+is needed to allow @command{tee} to continue to process the input
+to any remaining outputs.
+
 Since the above example writes to one file and one process,
 a more conventional and portable use of @command{tee} is even better:
 
@@ -13087,6 +13092,17 @@ tar chof - "$tardir" \
   | bzip2 -9 -c > your-pkg-M.N.tar.bz2
 @end example
 
+If you want to further process the output from process substitutions,
+and those processes write atomically (i.e., write less than the system's
+PIPE_BUF size at a time), that's possible with a construct like:
+
+@example
+tardir=your-pkg-M.N
+tar chof - "$tardir" \
+  | tee >(md5sum --tag) > >(sha256sum --tag) \
+  | sort | gpg --clearsign > your-pkg-M.N.tar.sig
+@end example
+
 @exitstatus