Korn shell question

[Bill Davidsen]

Don Russell wrote:
> On Wed, Apr 16, 2008 at 10:37 AM, Don Russell
> <fedora at drussell.dnsalias.com> wrote:
>>
>>
>>
>>
>>
>> On Wed, Apr 16, 2008 at 8:44 AM, Patrick O'Callaghan <pocallaghan at gmail.com> wrote:
>>
>>>
>>> On Wed, 2008-04-16 at 10:41 -0400, Bill Davidsen wrote:
>>>> Patrick O'Callaghan wrote:
>>>>> On Tue, 2008-04-15 at 10:49 -0700, Don Russell wrote:
>>>>>> How can I tell, from a Korn shell script, if the script is running in
>>>>>> a vi sub-shell?
>>>>>>
>>>>>> I have a script that has a problem when run from a vi subshell, and
>>>>>> I'd like to check for that condition and just issue an error message.
>>>>>> (I know that's not the solution to the problem, but the thing that
>>>>>> fails is being replaced, so this is a temporary "fix")
>>>>> Try:
>>>>>
>>>>> ls -l /proc/`cat /proc/$$/status|grep PPid|cut -f2`/exe
>>>> What on Earth are you doing here?
>>>> 1) unless you have some reason to doubt the value of $PPID, you are just
>>>>     making this look complex
>>>> 2) if this is a login shell, you will not have permission to read the
>>>>     exe symbolic link.
>>>> 3) you probably just want to see if /proc/$PPIC/cmdline matches vi
>>> Duh, yes. The OP wants to know if his script is being executed from
>>> 'vi'. That's one way to do it. You're right about the permissions of
>>> course, my bad, but using $PPID doesn't change that in the script.
>>>
>>> Here's a better one:
>>>
>>> ps -p $PPID -o comm=
>>>
>>>
>> That's GREAT! It's exactly what I need.... and bonus points for it working on other platforms too ;-)
> 
> I spoke too soon... I had to tweak it a little.... since running the
> script starts a new shell, it's not enough to look at the parent... I
> have to go back a generation further to look at the Grand Parent
> PID...
> 
> Thus, in the script that cares about such things...
> 
> GPPID=`/usr/bin/ps -p $PPID -oppid=`
> if [[ "LOGINSHELL" != `/usr/bin/ps -p $GPPID -o comm=` ]]; then
>      print "$0 not allowed from sub-shell" >&2
>      exit 1
> fi
> 
> Of course the LOGINSHELL literal could be system specific...
> 
Sounds like a job for $SHLVL

-- 
Bill Davidsen <davidsen at tmr.com>
   "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot