This is not the fault of Linux. It's an unavoidable consequence of the way
the shebang-line is defined in various standards. In fact, I'm the guy who
fixed FreeBSD to comply with those standards, and thus I deliberately
changed the way FreeBSD handled shebang lines from "convenient" to
"broken". For reasons which might not be intuitively obvious, the broken
behavior is required.
Since FreeBSD *used* to process the shebang line in a more convenient
way, I also came up with some changes to /usr/bin/env which can be used
to recreate the more convenient problem. However, those new options are
only available on FreeBSD (afaik).
I also have to write ruby or perl scripts which have to work on a variety of
unix-based operating systems. What I have come up with is the following.
I'm sure that it will not work on some operating system, but it works on the
dozen operating systems that I have to care about, in all situations that I
have cared about.
#!/bin/sh
# -------+---------+---------+-------- + --------+---------+---------+---------+
# / This section is a safe way to find the interpretter for ruby, \
# | without caring about the user's setting of PATH. This reduces |
# | the problems from ruby being installed in different places on |
# | various operating systems. A much better solution would be to |
# | use `/usr/bin/env -S-P' , but right now `-S-P' is available |
# \ only on FreeBSD 5, 6 & 7. Garance/2005 /
OSRUBYBIN=
for fname in /usr/local/bin /opt/csw/bin /opt/local/bin /usr/bin ; do
if [ -x "$fname/ruby" ] ; then OSRUBYBIN="$fname/ruby" ; break; fi
done
if [ -z "$OSRUBYBIN" ] ; then
echo "Unable to find a 'ruby' interpretter!" >&2
exit 1
fi
eval 'exec "$OSRUBYBIN" -x -S $0 ${1+"$@"}'
echo "The 'exec \"$OSRUBYBIN\" -x -S ...' failed!" >&2
exit 1
#! This #!-line starts the real script, due to the marker: ruby
....[ and then the first line of the real ruby script]...
Obviously you could add the '-w' after '-x' on the eval/exec line, if you
also wanted that option. And if you do something weird like install
'ruby' in /bin (so that you can find out when /usr is not mounted), then
you'd need to add that to the list of directories which are searched.
In some cases, I also set a new value for PATH= in the /bin/sh
portion of the script, to avoid ruby's warning about an "Insecure
world writable dir". That warning message can also be avoided
by setting $VERBOSE in the ruby script, but in some cases it's
just easier for me to change the value for PATH.
I suspect that all this is too esoteric for most people to other with! 
It really is rather absurdly complicated to get 100% right in 100% of
the situations that every ruby script might be run in.
···
On 1/31/07, Eric Hodel <drbrain@segment7.net> wrote:
On Jan 31, 2007, at 08:45, Rob Sanheim wrote:
> I'm trying to convert some bash scripts to use /usr/bin/env ruby
> instead of hardcoded shebang lines, and running into an issue. Using
> this:
>
> #!/usr/bin/env ruby -w
>
> results in this error:
>
> /usr/bin/env: ruby -w: No such file or directory
>
> If I remove the -w, it runs and works fine. But of course, I want
> the warnings check in there...
Linux's env/shebang is broken, so you can't use the shebang this
way. It decides "ruby -w" is the name of the thing you want to
lookup, and of course env can't find that because there isn't one.
--
Garance Alistair Drosehn = drosihn@gmail.com
Senior Systems Programmer
Rensselaer Polytechnic Institute; Troy, NY; USA
