Feature #6648

Provide a standard API for retrieving all command-line flags passed to Ruby

Added by headius (Charles Nutter) about 5 years ago. Updated over 4 years ago.

Target version:


Currently there are no standard mechanisms to get the flags passed to the currently running Ruby implementation. The available mechanisms are not ideal:

  • Scanning globals and hoping they have not been tweaked to new settings
  • Using external wrappers to launch Ruby
  • ???

Inability to get the full set of command-line flags, including flags passed to the VM itself (and probably VM-specific) makes it impossible to launch subprocess Ruby instances with the same settings.

A real world example of this is "((%bundle exec%))" when called with a command line that sets various flags, a la ((%jruby -Xsome.vm.setting --1.9 -S bundle exec%)). None of these flags can propagate to the subprocess, so odd behaviors result. The only option is to put the flags into an env var (((|JRUBY_OPTS|)) or ((|RUBYOPT|))) but this breaks the flow of calling a simple command line.

JRuby provides mechanisms to get all its command line options, but they require calling Java APIs from Ruby's API set. Rubinius provides its own API for accessing comand-line options, but I do not know if it includes VM-level flags as well as standard Ruby flags.

I know there is a (({RubyVM})) namespace in the 2.0 line. If that namespace is intended to be general-purpose for VM-level features, it would be a good host for this API. Something like...

class << RubyVM
def vm_args; end # returns array of command line args not passed to the target script

def script; end # returns the script being executed...though this overlaps with $0

def script_args; end # returns args passed to the script...though this overlaps with ARGV, but that is perhaps warranted since ARGV can be modified (i.e. you probably want the original args)


Related issues

Is duplicate of Ruby trunk - Feature #4046: Saving C's **argv and cwd allows Ruby programs to reliably restart themselvesFeedback2010-11-12


#1 [ruby-core:45868] Updated by headius (Charles Nutter) about 5 years ago

Oops, this should be a feature request.

#2 Updated by nobu (Nobuyoshi Nakada) about 5 years ago

  • Tracker changed from Bug to Feature

I'm positive to the feature, but RubyVM wouldn't be right place.
It is CRuby specific and unexpected to be in other implementations.

#3 [ruby-core:45870] Updated by nobu (Nobuyoshi Nakada) about 5 years ago

  • Description updated (diff)

#4 Updated by headius (Charles Nutter) almost 5 years ago

ARGV is a special class; perhaps ARGV could have the methods?

#5 [ruby-core:47608] Updated by headius (Charles Nutter) almost 5 years ago

I was is ARGF, not ARGV that is a special class. ARGV is a normal array.

Another option: ENV, which is a special Hash-like class. ENV.vm_args, ENV.script, and ENV.script_args aren't bad.

#6 [ruby-core:47984] Updated by headius (Charles Nutter) almost 5 years ago

Ping...we'd still like to have this to be able to build a unifying benchmark tool, which needs to be able to report the actual command-line arguments passed to the runtime. Current tricks are too ugly (parsing ps output, for example), and this would not be difficult to add.

I'm leaning toward ENV having a few special methods for this, but I'm open to other ideas.

#7 [ruby-core:49917] Updated by mame (Yusuke Endoh) over 4 years ago

  • Status changed from Open to Assigned
  • Assignee set to matz (Yukihiro Matsumoto)
  • Target version set to next minor

I'm sorry that matz didn't noticed this.

Yusuke Endoh

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