Date: Sat, 21 Mar 1998 16:10:01 -0800 (PST) From: Martin Cracauer <cracauer@cons.org> To: freebsd-bugs Subject: Re: bin/6087: sh doesn't work properly on certain configuration scripts Message-ID: <199803220010.QAA26509@hub.freebsd.org>
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The following reply was made to PR bin/6087; it has been noted by GNATS. From: Martin Cracauer <cracauer@cons.org> To: giffunip@asme.org Cc: freebsd-gnats-submit@FreeBSD.ORG Subject: Re: bin/6087: sh doesn't work properly on certain configuration scripts Date: Sun, 22 Mar 1998 01:07:04 +0100 In <199803211955.LAA15097@hub.freebsd.org>, giffunip@asme.org wrote: > While using a configure script a problem with FreeBSD's sh was revealed. > The author of the script claims this is not a bash specific feature. > TBH Solaris doesn't have this bug either > >How-To-Repeat: > #!/usr/bin/sh > > foobar="" > if test -n ""$foobar; then > echo "Help, I am broken" > fi Our /bin/sh expands ""$foobar to nothing, not to the empty string. I can't really judge over this, but it seems obvious that it should be the empty string and that we need to fix this. But there's another "interesting" detail in here: What does `test -n` return when no additional argument is passed? FreeBSD's /bin/test (and bash2's) is supposed to support a call syntax test string without any option switch, which is supposed to return true if strings is not an empty string. That way, '-n' without an argument can be considered a non-empty string passed without option keys and true can be returned, which is what it does for now. ~(waldstrasse)44% bash -c 'test "" ; echo $?' 1 ~(waldstrasse)45% bash -c 'test "n" ; echo $?' 0 ~(waldstrasse)46% bash -c 'test "-n" ; echo $?' 0 ~(waldstrasse)47% bash -c 'test "-n" ""; echo $?' 1 ~(waldstrasse)48% bash -c 'test "-n" "n"; echo $?' 0 FreeBSD's /bin/test returns the same. Solaris' removed the non-switch syntax from from the manpage for /bin/test, while the actual program still supports it (Solaris 2.5). If the string is what could be a switch, it is considered an error to be called with no additional argument. This is for the external program /bin/test, which is really an alias for /bin/ksh. You won't beleive how slow it is... ~(waldstrasse)32% /bin/test "" ; echo $? 1 ~(waldstrasse)33% /bin/test "n" ; echo $? 0 ~(waldstrasse)34% /bin/test "-n" ; echo $? /bin/test[8]: test: argument expected 2 ~(waldstrasse)35% /bin/test "-n" ""; echo $? 1 ~(waldstrasse)36% /bin/test "-n" "n"; echo $? 0 To make things worse, there is a bug in Solaris' /bin/sh built-in test: The intended behaviour seems to be exactly the same as for /bin/test. But it has a bug in that the whole script is terminated when `test -n` fails, see the third test, the echo command isn't executed. Someone obviously does an exit(1) here... ~(waldstrasse)22% /bin/sh -c 'test "" ; echo $?' 1 ~(waldstrasse)23% /bin/sh -c 'test "n" ; echo $?' 0 ~(waldstrasse)24% /bin/sh -c 'test "-n" ; echo $?' /bin/sh: test: argument expected ~(waldstrasse)25% /bin/sh -c 'test "-n" ""; echo $?' 1 ~(waldstrasse)26% /bin/sh -c 'test "-n" "n"; echo $?' 0 Could someone please look up the Posix standard for test(1)? I'm working on other syntax bugs of FreeBSD's /bin/sh and will add the expansion issue from above, but I can't promise anything soon. This is a very difficult area. For every sh bug in a given Unix clone you can bet that many places in the same OS depend on it. Martin -- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Martin Cracauer <cracauer@cons.org> http://www.cons.org/cracauer BSD User Group Hamburg, Germany http://www.bsdhh.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-bugs" in the body of the message
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