Korn shell question

[Don Russell]

On Tue, Apr 15, 2008 at 5:51 PM, Patrick O'Callaghan <pocallaghan at gmail.com>
wrote:

>
> On Tue, 2008-04-15 at 16:56 -0700, Don Russell wrote:
> >
> >
> > On Tue, Apr 15, 2008 at 4:17 PM, Cameron Simpson <cs at zip.com.au>
> > wrote:
> >
> >         On 15Apr2008 12:09, Don Russell <fedora at drussell.dnsalias.com>
> >         wrote:
> >         | On Tue, Apr 15, 2008 at 11:08 AM, Patrick O'Callaghan
> >         <pocallaghan at gmail.com>
> >         | 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
> >         | > and work from there.
> >         |
> >         | That looks promising... thanks :-)
> >
> >
> >         Promising, but will work only on Linux. That may be enough for
> >         you, but you
> >         shouldn't forget that it's nonportable.
> >
> > I just tried this on a Linux system... it makes sense... I tried it on
> > a UNIX (AIX) system, and it did not help directly. On UNIX the status
> > file appears to be "raw" binary data that maps to a C structure...
> > could get tricky trying to extract the correct parts.
>
> I'm amazed it even exists on AIX. I was assuming you meant Linux (this
> is a Fedora list after all).
>

Yes, and some of the most Unix/Linux knowledgeable people I know. :-)


>
> > On Linux, it looks like that decoding is all done and present in
> > human-readable terms. :-)
> >
> >
> >
> >
> >         You can probably make that `cat|grep|cut` into a single `sed`
> >         at some
> >         performance benefit.
> >
> >         Another approach is to alter your shell environment to always
> >         set and export
> >         an environment variable when starting vi (by invoking vi via a
> >         wrapper script
> >         or alias or shell function) and then just checking for it.
> >
> > Though simple, that's not an option for me.... I can't "wrap" vi...
>
> You can. Just put the wrapper in $HOME/bin and set PATH=$HOME/bin:$PATH,
> e.g.
>
> $ cat $HOME/vi
> #!/bin/sh
>
> export MY-SPECIAL-FLAG=1
> exec /usr/bin/vi $*
> $
>
>
Well, yes, I can do it for me, but I'm not in a position to do it for all
the other users of the system to which I do not have root access. I *do*
have control over the script they all use, which is why I want to detect "in
a sub-shell" from that script, then I can just exit with an error message...

You've given me some good information... I just might have to decode the raw
binary data on AIX instead of having the friendly text as seen on Linux. :-)


In the mean time, if people complain that it fails when run from a
sub-shell, I just reply with "don't run it from a sub-shell". :-)

And maybe before too long, the whole point will be moot because the part
that breaks right now will be replaced...
Still, a fun exercise. :-)

Cheers
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