On Thu, Jun 27, 2013 at 7:55 PM, Todd Sterben <lists@r= uby-forum.com> wrote:

Thanks for the responses. =C2=A0I should hav= e been a bit more clear about my
UNIX skills. =C2=A0Not great, but I can move around and set permissions and=
look at things like environment variables. =C2=A0So I had already set thing= s
to execute. =C2=A0I still can't see what is up. =C2=A0Here is the code(= again) and
files and symbolic links & path & permissions

Here is my beautiful code:

#!/usr/bin ruby

Change that to: #!/usr/= bin/env ruby
=C2=A0

puts "Hello world!"

which produces these errors:

./test.rb: line 1: =EF=BB=BF#!/usr/bin: No such file or directory
./test.rb: line 3: puts: command not found

/usr/bin is in PATH so it should not have a problem there:

/usr/lib/lightdm/lightdm:
/usr/local/sbin:
/usr/local/bin:/usr/sbin:
/usr/bin:/sbin:/bin:
/usr/games:
/usr/bin/ruby

ruby points, through symbolic links, to /usr/bin/ruby1.9.1

lrwxrwxrwx 1 root root =C2=A0 22 Jun 20 16:30 ruby -> /etc/alternatives/= ruby

lrwxrwxrwx 1 root root 18 Jun 20 16:30 ruby -> /usr/bin/ruby1.9.1

-rwxr-xr-x 1 root root 5552 Mar 22 12:14 ruby1.9.1

And the code is here:

-rwxrwxrwx 1 john john 41 Jun 27 18:41 test.rb

I am going to /home/john to run the file ./test.rb

And everything is executable

--
Posted via http://= www.ruby-forum.com/.

Every= thing looks fine except for the one change I mentioned above.

With the shebang line, you are telling bash to e= xecute "/usr/bin/env", passing it one parameter, "ruby"= . The "env" program will then launch the appropriate "ruby&q= uot; executable.

The reason for this is that "sheb= ang" line must specify a complete path to an executable (either an abs= olute path or one relative to the current working directory; relative paths= are problematic though so everyone uses absolute paths). Since the "r= uby" executable may be installed in a different location on different = systems, the convention is to instead run ruby via the "env" comm= and for which it is safe to assume it'll be available in the /usr/bin d= irectory.

The "env" command lets you r= un other commands in a modified environment. However, in this case, it'= s just being used for the fact that it'll look up whatever command you = tell it to run using the PATH environment variable. So, as long as an execu= table (or a symlink to one) is in one of the directories in your PATH (whic= h is the case on your system) then "env" can run it.

You c= an try it manually inside your shell (the "^D" mean, type CTRL-D;= you won't actually see the "^D" characters):

$ /usr/bin/env ruby
puts "Hi"