Re: env: add -S option (split string for shebang lines in scripts)

[Eric Blake]

On 05/01/2018 10:47 AM, Bernhard Voelker wrote:
> > On Fri, Apr 27, 2018 at 12:57 PM, Eric Blake <address@hidden> wrote:
> > > This is missing support for -P, which is one of the essential features
> > > of FreeBSD env, per their man page:
> >
> > I can certainly add support "-P" (I'll do it in a separate patch though).
> >
> > Is "-P" (alternate path) something that is often requested?

It makes reasonable sense: the FreeBSD argument is that if you do

#!/usr/bin/env perl

you are at the mercy of finding perl on the user's current PATH, but if 
you do:

#!/usr/bin/env -S -P /usr/bin:/opt/bin:${PATH} perl

you can favor /usr/bin/perl or /opt/bin/perl first regardless of whether 
the user looks there normally, and without corrupting the user's own 
choice of perl for any child processes within the script.

> > I do see a lot of questions about passing multiple arguments with 
> > "#!/usr/bin/env",
> > but I haven't noticed people asking about setting per-script non-standard $PATH
> > (but without changing the actual $PATH).
>
> Isn't this the regular case with specifying the PATH variable?
>
>    env PATH=/some:/path prg

Close, but not quite the same.  -P can affect the lookup path without 
also leaking that changed lookup to the script itself.  You're right 
that if you call 'env PATH=...', that env has to look up prg within that 
specified PATH rather than the PATH in effect pre-env, but I can see 
cases where you want to find the interpreter at a known location but NOT 
change the PATH handed off to the final script.

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
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