Re: BUG: Shell builtin `which` prints non-existent commands to stdout

[Peter Stephenson <p.stephenson@xxxxxxxxxxx>]

On Mon, 24 Sep 2018 23:32:53 +0100
Stephane Chazelas <stephane.chazelas@xxxxxxxxx> wrote:
> About "other shells" above, AFAIK, tcsh is the only other shell
> that has a "which" builtin and it does also send "command not
> found" to stdout. So zsh behaves like every other shells in that
> regard.

Thanks, I've updated the text.

pws

diff --git a/Etc/FAQ.yo b/Etc/FAQ.yo
index 9f634d1..81d7628 100644
--- a/Etc/FAQ.yo
+++ b/Etc/FAQ.yo
@@ -1976,21 +1976,22 @@ sect(Why does `which' output for missing commands go to stdout?)
   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.
+  The original reason for this is that this behaviour is inherited from
+  previous versions of `tt(which)', a builtin in tcsh (an adaptation of
+  the C Shell with better editing) and also a separate script.  Other
+  shells had equivalent commands, `tt(whence)' and `tt(type), that zsh
+  has also adopted.  So in fact this has always been a feature of
+  `tt(which)'.  (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, 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)