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Test exit status misinterpreted in scripts when buit without job control


From: Dan Cross
Subject: Test exit status misinterpreted in scripts when buit without job control
Date: Thu, 04 Aug 2016 16:05:55 +0000

Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64' 
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-unknown-linux-gnu' 
-DCONF_VENDOR='unknown' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' 
-DSHELL -DHAVE_CONFIG_H   -I.  -I.. -I../include -I../lib   -g -O2
uname output: Linux spitfire.my.domain 3.13.0-88-generic #135-Ubuntu SMP Wed 
Jun 8 21:10:42 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
Machine Type: x86_64-unknown-linux-gnu

Bash Version: 4.3
Patch Level: 30
Release Status: release

Description:
        When bash is built without job control, shell scripts that use
        the 'test' builtin (e.g., via '[') in conditionals may take the
        wrong branch becuase the exit status of the test is lost.

Repeat-By:
        Configure without job control.  Via e.g.,
        ./configure --prefix=/usr --bindir=/bin --without-bash-malloc 
--disable-nls --disable-job-control
        Invoke the resulting shell and run the following sequence of commands:

        $ cat > foo.sh
        if [ $# -lt 2 ]
        then
                echo "$# args is less than 2"
        else
                echo "$# args is not less than 2"
        fi
        $ chmod +x ./foo.sh
        $ ./foo.sh 1 2 3 4
        4 args is less than 2
        $

        Observe the output: '4' is not actually less than '2' yet the
        script incorrectly reports it as such.

        Note: we originally discovered this when porting 'bash' to a
        new research operating system that does not support job control.
        However, we were able to reproduce on Linux.



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