ruby/rubygems · error · Gem::CommandLineError

Please specify a gem name or a .gem file on the command line

Error message

Please specify a gem name or a .gem file on the command line

What it means

Error "Please specify a gem name or a .gem file on the command line" thrown in ruby/rubygems.

Source

Thrown at lib/rubygems/commands/specification_command.rb:79

Specific fields in the specification can be extracted in YAML format:

  $ gem spec rake summary
  --- Ruby based make-like utility.
  ...

    EOF
  end

  def usage # :nodoc:
    "#{program_name} [GEM_OR_FILE] [FIELD]"
  end

  def execute
    specs = []
    gem = options[:args].shift

    unless gem
      raise Gem::CommandLineError,
            "Please specify a gem name or a .gem file on the command line"
    end

    case v = options[:version]
    when String
      req = Gem::Requirement.create v
    when Gem::Requirement
      req = v
    else
      raise Gem::CommandLineError, "Unsupported version type: '#{v}'"
    end

    if !req.none? && options[:all]
      alert_error "Specify --all or -v, not both"
      terminate_interaction 1
    end

    if options[:all]

View on GitHub (pinned to 86cbb817a3)

When it happens

Trigger: Thrown at lib/rubygems/commands/specification_command.rb:79 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of ruby/rubygems@86cbb817a3 (2026-08-23). Data as JSON: /api/errors/b7907eff39af1eac. Report an issue: GitHub.