From: Peter Stephenson <p.stephenson@samsung.com>
To: Zsh Workers <zsh-workers@zsh.org>
Subject: Re: BUG: Shell builtin `which` prints non-existent commands to stdout
Date: Mon, 24 Sep 2018 13:51:24 +0100 [thread overview]
Message-ID: <20180924125126eucas1p2e4ae5b63ce6320957ee99737f93181ae~XVwcoX7b91518615186eucas1p2T@eucas1p2.samsung.com> (raw)
In-Reply-To: <20180924122933.gpzp4vfix6zl66nw@klaus.seistrup.dk>
On Mon, 24 Sep 2018 14:29:33 +0200
Klaus Alexander Seistrup <klaus@seistrup.dk> wrote:
> Peter Stephenson wrote:
>
> > This is not a bug and has been discussed numerous times
>
> Thanks, I hadn't see that. I'll just keep the `which` alias, then.
Might be useful to make the issue more visible...
diff --git a/Etc/FAQ.yo b/Etc/FAQ.yo
index a3dfc6c..e15e024 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 orignated. 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 outputing 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 status does
+ reflect the fact the command can't be found.
+
+
chapter(The mysteries of completion)
next prev parent reply other threads:[~2018-09-24 13:02 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20180924080113epcas4p4f8f89aa03a2cebc5030fd45dca0f6e84@epcas4p4.samsung.com>
2018-09-24 8:00 ` Klaus Alexander Seistrup
2018-09-24 10:22 ` Peter Stephenson
2018-09-24 12:29 ` Klaus Alexander Seistrup
2018-09-24 12:51 ` Peter Stephenson [this message]
2018-09-24 13:22 ` [PATCH] zshbuiltins(1): Document 'which''s "not found is not an error" behaviour Daniel Shahaf
2018-09-24 22:18 ` BUG: Shell builtin `which` prints non-existent commands to stdout Stephane Chazelas
2018-09-25 7:56 ` Stephane Chazelas
2018-09-24 22:32 ` Stephane Chazelas
2018-09-25 9:10 ` Peter Stephenson
[not found] ` <20180924112218.7bac7f2c@camnpupstephen.cam.scsc.local>
2018-09-24 10:25 ` Peter Stephenson
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