[olug] Odd results from /bin/sh (GNU bash) and the "test" command...

[Kevin]

Don't know what's going on, but my linux system(RHEL5.1/CentOS5.3
hybrid) gives the correct behavior as a normal user, but the incorrect
behavior as root.


On Thu, Feb 25, 2010 at 11:38, Dan Linder <dan at linder.org> wrote:
> I was debugging a script (CentOS 5.4 with all updated patches) that
> was spewing errors to the screen.  The errors came from a simple "cat
> /path/filename" and cat was reporting "Permission denied", and the
> file had only a write permission:
>
> # ls -al /sys/bus/pci/drivers_probe
> --w------- 1 root root 4096 Feb 25 10:05 /sys/bus/pci/drivers_probe
>
> The "test" (or [ ]) command has the -r option:
>        -r FILE
>               FILE exists and read permission is granted
>
> But a quick test shows that "-r" is saying this file is readable:
>
> #!/bin/sh
> set -x
> FILE=/tmp/notreadable
> touch $FILE
> chmod a-rwx $FILE
> ls -al $FILE
> if [ -r $FILE ] ; then
>     echo Readable test 1
> else
>     echo NOT Readable test 1
> fi
>
> # /tmp/testread
> + FILE=/tmp/notreadable
> + touch /tmp/notreadable
> + chmod a-rwx /tmp/notreadable
> + ls -al /tmp/notreadable
> ---------- 1 root root 0 Feb 25 11:04 /tmp/notreadable
> + '[' -r /tmp/notreadable ']'
> + echo Readable test 1
> Readable test 1
>
> I haven't found if this is a bug or an odd 'quirk', but it happens as
> both a normal user and as root.
>
> If I'm using it incorrectly please tell me, or keep this in the back
> of your mind if you have an odd script action...
>
> Very weird...still investigating it.
>
> Dan
>
> --
> ***************** ************* *********** ******* ***** *** **
> "Quis custodiet ipsos custodes?"
>    (Who can watch the watchmen?)
>    -- from the Satires of Juvenal
> "I do not fear computers, I fear the lack of them."
>    -- Isaac Asimov (Author)
> ** *** ***** ******* *********** ************* *****************
> _______________________________________________
> OLUG mailing list
> OLUG at olug.org
> https://lists.olug.org/mailman/listinfo/olug
>