Date: Tue, 4 Mar 1997 18:25:12 -0800 (PST) From: fenner@parc.xerox.com To: FreeBSD-gnats-submit@freebsd.org Subject: bin/2879: sh: ! fails to negate the return value of a pipeline Message-ID: <199703050225.SAA15291@thud.FreeBSD.org> Resent-Message-ID: <199703050230.SAA11773@freefall.freebsd.org>
next in thread | raw e-mail | index | archive | help
>Number: 2879
>Category: bin
>Synopsis: sh: ! fails to negate the return value of a pipeline
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Tue Mar 4 18:30:02 PST 1997
>Last-Modified:
>Originator: Bill Fenner
>Organization:
Xerox
>Release: FreeBSD 3.0-970209-SNAP i386
>Environment:
/bin/sh from -current (2.2 is not (yet?) affected)
>Description:
! fails to negate the return value of a pipeline. The sh man page says:
If the reserved word ! does not precede the pipeline, the
exit status is the exit status of the last command speci-
fied in the pipeline. Otherwise, the exit status is the
logical NOT of the exit status of the last command.
However, I see the following behavior:
$ if ! date | false; then echo hi; fi
$ if ! date | true; then echo hi; fi
hi
! works when not associated with a pipeline:
$ if ! false; then echo hi; fi
hi
$ if ! true; then echo hi; fi
All of the above work properly in 2.2 .
>How-To-Repeat:
Use ! to negate the return value of a pipeline. Watch it fail to negate
the return value of the pipeline.
>Fix:
I'm pretty suspicious of rev 1.17 of parser.c, since it appears to
change where in the parse tree the NNOT (23) appears.
In 2.2, the parse tree for the command line "! date | false" looks
something like
evaltree(0x539cc: 23) called [!]
evaltree(0x53988: 2) called [|]
evaltree(0x53978: 1) called [date]
evaltree(0x539bc: 1) called [false]
In 3.0, the parse tree for the same command line looks like
evaltree(0x19b54: 2) called [|]
evaltree(0x19b4c: 23) called [!]
evaltree(0x19b3c: 1) called [date]
evaltree(0x19b88: 1) called [false]
e.g. it looks like the return value of date is being negated and
then discarded. Presumably there was a reason to make the changes
in 1.17, and since I don't understand that reason I can't suggest
a fix (other than back them out).
>Audit-Trail:
>Unformatted:
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199703050225.SAA15291>