Re: Bug-bash Digest, Vol 47, Issue 9

[Thomas Mellman]

bug-bash-request@gnu.org wrote:

> -------
>
> Message: 1
> Date: Tue, 10 Oct 2006 16:08:05 -0500
> From: mwoehlke <mwoehlke@tibco.com>
> Subject: How to detect bash?
> To: bug-bash@gnu.org
> Message-ID: <egh23l$i6c$1@sea.gmane.org>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Anyone have any clever, VERY reliable tricks for detecting if the 
> current shell is bash? The obvious way is '[ -n "$BASH" ]', but in the 
> interest of catching idiots that set BASH to get around such a check, I 
> came up with:
>
> [ "`BASH_SUBSHELL=975 ; ( echo $BASH_SUBSHELL )`" -eq 976 ]
>
> (975 is of course an arbitrary number.)
>
> Anyone think they know a better way (or a reason the above might not 
> work)? I'm guessing it can still be circumvented*, but one would have to 
> be specifically making an effort to do so.
>
> (* Actually, I'm not 100% certain it can; you have to be able to run a 
> script upon sub-shell startup. I'm assuming that can be done, but maybe 
> I'm wrong...)
>
>  

I have this.  I don't like it, but I don't know any better.

getshelltype ()
{
   #
   # unfortunately, using set -o options doesn't work here
   #
   if typeset -Z a 2> /dev/null; then
       echo ksh
   else
       echo bash
   fi
}