linux-kernel - Re: Hi all, bug or design flaw?

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Date:	Thu, 21 Jan 2010 21:15:30 -0500
From:	Daniel Hazelton <dhazelton@...er.net>
To:	Shu Wu <superwushu@...il.com>
Cc:	Stepan Chatalyan <kehcho@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: Hi all, bug or design flaw?

On Thursday 21 January 2010 09:00:15 pm Shu Wu wrote:
> Hey, buddy, this is not the right place to raise a user-space
> question. But as for your question, you'd better to learn what the "."
> means. "#!/bin/bash" is used to indicate in shell when executed, while
> to be just a comment in the latter.
> 
> 2010/1/22 Stepan Chatalyan <kehcho@...il.com>:
> > Hi there,
> >
> > I'm Stepan G. Chatalyan, and i think that I discovered a bug or design
> > flaw... and I don't know that it is provide from kernel...
> >
> > Let's see:
> >
> > (1) I mount /tmp with noexec,nosuid,nodev options
> >
> > /dev/hda6 on /tmp type ext3 (rw,noexec,nosuid,nodev,relatime)
> >
> > (2) I went to 'cd /tmp'`and I created a bash script, or another script
> > (perl, python, etc)... and chmod +x createdfile
> > script cointain:
> >
> > #!/bin/bash
> > echo "Probe..."
> >
> > (3) I tried to execut it with "./createdfile"
> > [kehcho@...cho] [/tmp]$ ./createdfile
> > -bash: ./createdfile: /bin/bash: bad interpreter: Permission denied
> >
> > (4) I tried to execute it, but pass to bash ". /tmp/createdfile"
> >
> > [kehcho@...nadowt] [/tmp]$ . /tmp/createdfile
> > Probe...
> >
> > It is a kernel bug or I just report a another one?

This is not a bug at all. I'll just repeat Shu Wu's statement - learn what "." 
actually does. Note: it is *NOT* the same as $(...) or `...` - and it is not 
the same as directly executing a script.

DRH
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