How can same program in ruby accept input from user as well as command line arguments

Question

My ruby script gets certain inputs from command line arguments. It check if any of the command line argument is missing, then it prompts for an input from user. But i am not able to get input from user using gets.

Sample code: test.rb

name=""
ARGV.each do|a|
    if a.include?('-n')
        name=a
        puts "Argument: #{a}"
    end
end
if name==""
    puts "enter name:"
    name=gets
    puts name
end

Running script: ruby test.rb raghav-k

Results in the error:

test.rb:6:in `gets': No such file or directory - raghav-k (Errno::ENOENT)
    from test.rb:6:in `gets'
    from test.rb:6:in `<main>'

Any pointers in this direction will be really grateful Thanks Sandy

Martin Tournoij · Accepted Answer · 2014-12-12 23:57:20Z

13

gets will only read from the real $stdin (ie the user) if there are no command line arguments. Otherwise it'll take those arguments as files to concatenate as a virtual $stdin.

You can use STDIN.gets to make sure you're always using the right function.

You can also delete the arguments from ARGV as you go (or remove them all in one go), your gets should work correctly.

edited Dec 12, 2014 at 23:57

Martin Tournoij

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answered Sep 13, 2011 at 9:55

rjp

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3 Comments

Augusto Over a year ago

+1 Definitely a non-intuitive behaviour! I just found out that the correct way of reading from stdin is $stdin.gets

rjp Over a year ago

Yeah, that's the explicit way of forcing it to read from $stdin (which will probably avoid your arguments problem, I think.)

sandy Over a year ago

rjp: thanks for your inputs @Augusto: thanks. Using $stdin, it works perfectly...:):)

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