From e9a75f4bc70f4990775899d22fa298039de73ef5 Mon Sep 17 00:00:00 2001
From: Peter Stephenson
Date: Mon, 24 Sep 2018 14:34:31 +0100
Subject: 43527, tweaked: describe which output behaviour in FAQ.
---
Etc/FAQ.yo | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)
(limited to 'Etc/FAQ.yo')
diff --git a/Etc/FAQ.yo b/Etc/FAQ.yo
index a3dfc6c13..9f634d14a 100644
--- a/Etc/FAQ.yo
+++ b/Etc/FAQ.yo
@@ -127,6 +127,7 @@ Chapter 3: How to get various things to work
3.26. Why is my output duplicated with `tt(foo 2>&1 >foo.out | bar)'?
3.27. What are these `^' and `~' pattern characters, anyway?
3.28. How do I edit the input buffer in $EDITOR?
+3.29. Why does `which' output for missing commands go to stdout?
Chapter 4: The mysteries of completion
4.1. What is completion?
@@ -1964,6 +1965,34 @@ label(328)
quitting the editor will only return to zsh's command-line editing mode.
+sect(Why does `which' output for missing commands go to stdout?)
+
+ The issue is that if you run:
+ verb(
+ which non-existent-command
+ )
+ the error message goes, unusually, to standard output rather than
+ to standard error. Other shells send this message to standard error,
+ as they would if the command was about to be executed but could not be
+ found.
+
+ The original reason for this is that this behaviour is inherited
+ from the C shell (csh), where `tt(which)' itself originated. So
+ it has been in zsh a very long time, and it is now a feature.
+ (It would be possible to change this in emulation modes; however.
+ so far this possibility has been seen has more of an additional
+ confusion than a help.)
+
+ If you want some further rationalisation, which may be what the C
+ shell designers had in mind, you might note that `tt(which)' is
+ designed as a way of outputting information about a command. So
+ `this command can be found in ...' and `this command can't be found'
+ are both bits of information here, unlike the case where the command
+ is to be executed. So although it differs from other Bourne-style
+ shells it is in fact self-consistent. Note that the exit status does
+ reflect the fact the command can't be found.
+
+
chapter(The mysteries of completion)
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