How to pass parameters to ruby command line script

Question

I pass script to ruby via STDIN. E.g.,

$ ruby << EE
> puts "args: #{ARGV}"
> EE
args: []
$ ruby << EE
> puts "args: #{ARGV}"
> EE 'arg1' 'arg2'
> EE
-:2: syntax error, unexpected tSTRING_BEG, expecting keyword_do or '{' or '('
EE 'arg1' 'arg2'
    ^
$ ruby 'arg1' 'arg2' << EE
> puts "args: #{ARGV}"
> EE
ruby: No such file or directory -- arg1 (LoadError)
$ ruby -- 'arg1' 'arg2' << EE
> puts "args: #{ARGV}"
> EE
ruby: No such file or directory -- arg1 (LoadError)
$ ruby -e << EE
> puts "args: #{ARGV}"
> EE
ruby: no code specified for -e (RuntimeError)
$

I do not know how to pass parameters in this situation. The -e option doesn't get what's passed to STDIN. According to man page, the syntax is:

ruby ... [--] [prog_file] [args]

but my prog_file is on STDIN.

Santhosh · Accepted Answer · 2016-01-25 16:55:34Z

3

You can pass parameters like this

ruby << EE "" arg1 arg2
> puts ARGV.inspect
> EE
# ["arg1", "arg2"]

The "" is for a ruby file path, or in this case - empty.

edited Jan 25, 2016 at 16:55

answered Jan 25, 2016 at 16:47

Santhosh

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Comments

Stefan · Accepted Answer · 2016-01-25 17:21:54Z

2

Like many other Unix utilities, ruby recognizes - as a special filename for STDIN:

$ echo "p ARGV" | ruby - foo bar
["foo", "bar"]

or:

$ ruby - foo bar << EE
> p ARGV
> EE
["foo", "bar"]

or: (pressing controlD to end the input)

$ ruby - foo bar
p ARGV
["foo", "bar"]

edited Jan 25, 2016 at 17:21

answered Jan 25, 2016 at 16:59

Stefan

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2 Comments

Kashyap Over a year ago

Thanks. Is this documented somewhere?

Stefan Over a year ago

@Kashyap I can't find it in the Ruby documentation, but the Pickaxe book mentions it in Ruby and Its World

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