Question

I want to run perl -w using env. That works fine on the command line:

$ /bin/env perl -we 'print 'Hello, world!\n'' Hello, world! 

But it doesn’t work on the shebang line in a script:

#!/bin/env perl -w print 'Hello, world!\n'; 

Here is the error:

/bin/env: perl -w: No such file or directory 

Apparently env doesn’t understand the -w flag that I’m passing to perl. What’s wrong?

Answer 1

The hash-bang isn’t a normal shell command-line, the parsing and white-space handling is different – that’s what you’ve hit. See:

• http://www.in-ulm.de/~mascheck/various/shebang/
• http://homepages.cwi.nl/~aeb/std/hashexclam-1.html#ss1.3
• http://en.wikipedia.org/wiki/Shebang_(Unix)

Basically many/most unixes put all of the remaining text after the first space into a single argument.

So:

#!/bin/env perl -w 

is the equivalent of:

/bin/env 'perl -w' 

so you need to handle any options to the perl interpreter in some other fashion. i.e.

use warnings; 

(as @Telemachus)