From 877ca5bf8588ae73a6ccc672e41f13c5b3943b14 Mon Sep 17 00:00:00 2001
From: Pádraig Brady <P@draigBrady.com>
Date: Thu, 27 Jan 2011 07:17:16 +0000
Subject: join: don't report disorder against an empty file

This allows one to use join as a field extractor like:
  join -a1 -o 1.3,1.1 - /dev/null

* src/join.c (join): Don't flag unpairable lines when
one of the files is empty.
* tests/misc/join: Add a new test for empty input, and adjust
a previous test that was only checking against empty input.
* doc/coreutils.texi (join invocation): Document the change.
* NEWS: Likewise.
---
 doc/coreutils.texi | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

(limited to 'doc/coreutils.texi')

diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index d6e98c6d6..b89147ea8 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -4787,11 +4787,17 @@ If there is an error it exits with nonzero status.
 @macro checkOrderOption{cmd}
 If the @option{--check-order} option is given, unsorted inputs will
 cause a fatal error message.  If the option @option{--nocheck-order}
-is given, unsorted inputs will never cause an error message.  If
-neither of these options is given, wrongly sorted inputs are diagnosed
-only if an input file is found to contain unpairable lines.  If an
-input file is diagnosed as being unsorted, the @command{\cmd\} command
-will exit with a nonzero status (and the output should not be used).
+is given, unsorted inputs will never cause an error message.  If neither
+of these options is given, wrongly sorted inputs are diagnosed
+only if an input file is found to contain unpairable
+@ifset JOIN_COMMAND
+lines, and when both input files are non empty.
+@end ifset
+@ifclear JOIN_COMMAND
+lines.
+@end ifclear
+If an input file is diagnosed as being unsorted, the @command{\cmd\}
+command will exit with a nonzero status (and the output should not be used).
 
 Forcing @command{\cmd\} to process wrongly sorted input files
 containing unpairable lines by specifying @option{--nocheck-order} is
@@ -5672,7 +5678,9 @@ c c1 c2
 b b1 b2
 @end example
 
+@set JOIN_COMMAND
 @checkOrderOption{join}
+@clear JOIN_COMMAND
 
 The defaults are:
 @itemize
-- 
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