Bug 5338

Summary:	tcsh && is not short circuiting
Product:	[Retired] Red Hat Linux	Reporter:	jfoster
Component:	tcsh	Assignee:	Nalin Dahyabhai <nalin>
Status:	CLOSED NOTABUG	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	6.0	CC:	goeran
Target Milestone:	---
Target Release:	---
Hardware:	i386
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2002-03-25 05:38:22 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:

Description jfoster 1999-09-23 20:26:07 UTC

Running the following script yields the error "X11:
Undefined variable," whereas it should exit normally.

-----------------------------------------------------
#!/bin/tcsh

unsetenv X11
if ($?X11 && ($X11 == "huh?")) then
   echo "a"
endif
echo "b"
-----------------------------------------------------

Comment 1 Jeff Johnson 2000-01-10 20:48:59 UTC

This bug is still present in tcsh-6.09-1.

Comment 2 Göran Uddeborg 2001-07-17 21:30:25 UTC

This is not a bug, is it?  Variable expansion takes place in one step for a
complete line, before any evaluation of the expression or execution of command. 
As far as I'm aware, it has always been necessary to do

if ($?X11) then
   if ($X11 == "huh?") then
      echo "a"
   endif
endif

to achieve the desired effect.  Both in tcsh and in the original csh.

Comment 3 jfoster 2001-07-17 22:40:06 UTC

OK, it's a feature then.

Comment 4 Ben Liblit 2001-07-18 00:12:15 UTC

The reported behavior is surprising but correct.  Read "Csh Programming
Considered Harmful", section 6 (Expression Evaluation). 
<http://www.perl.com/pub/a/language/versus/csh.html>