How to run Ruby script with env and warnings enabled?

Question

I prefere to invoke Ruby scripts with a hash bang line using #!/bin/env ruby which allows me to use a local Ruby installation without conflicting with the systems Ruby installation. But how can I enable warnings on Linux systems? My test script:

#!/usr/bin/env ruby -w FOO

On Mac I get:

maasha@mel:~$ ./test.rb ./test.rb:3: warning: possibly useless use of a constant in void context ./test.rb:3:in `<main>': uninitialized constant FOO (NameError)

On Linux I get:

maasha@orsted:~$ ./test.rb /usr/bin/env: ruby -w: No such file or directory

I have noted the possibility to set export RUBYOPT=-w, but I would like to avoid that if possible. — maasha
– maasha, Commented Feb 21, 2013 at 10:58
There is a thread on the topic on ruby forum: ruby-forum.com/topic/96121 — maasha
– maasha, Commented Feb 21, 2013 at 11:11
More on env and multiple arguments here: stackoverflow.com/questions/4303128/… — maasha
– maasha, Commented Feb 21, 2013 at 11:13

Community · Accepted Answer · 2017-05-23 11:46:33Z

3

#!/usr/bin/env RUBYOPT=-w ruby

As suggested in this answer, this answer, and other places

edited May 23, 2017 at 11:46

CommunityBot

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answered May 27, 2016 at 16:03

ShadSterling

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4 Comments

maasha Over a year ago

Oh, and now you tell me! After 3 years! ;o)

ShadSterling Over a year ago

Sorry, I just hadn't see your question before - or found an answer, I just went looking again and this time found both

ShadSterling Over a year ago

... apparently that doesn't work on all systems, so here's another method: make your first non-comment line $VERBOSE = true

maasha Over a year ago

You better add that as a separate answer.

ShadSterling · Accepted Answer · 2016-07-03 00:51:02Z

My first answer doesn't work on all systems, so here's another method: make your first non-comment line

$VERBOSE = true

which is What the -w switch does. From http://linux.die.net/man/1/ruby:

-v'

--verbose' Enables verbose mode. Ruby will print its version at the beginning, and set the variable $VERBOSE to true. Some methods print extra messages if this variable is true. If this switch is given, and no other switches are present, Ruby quits after printing its version.

-w' Enables verbose mode without printing version message at the beginning. It sets the $VERBOSE variable to true.

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