Detecting stdin content in Ruby

Question

I want to know whether or not someone is trying to give a ruby program content on stdin. I do not want ruby to fall back to allowing interactive input. How do I do this?

# When called in bash like this, I want 'cat.rb' to exit immediately:
ruby cat.rb

# When called in bash like this, I want to see the word 'hello':
echo hello | ruby cat.rb

If I just have cat.rb contain puts gets then the first example will block, waiting for an EOF on interactive stdin. I don't want to modify the calling command, but wish to support both kinds of behavior.

dpst · Accepted Answer · 2018-03-15 18:40:13Z

5

Look at $stdin.tty?

ruby cat.rb
# $stdin.tty? -> true

echo hello | ruby cat.rb
# $stdin.tty? -> false

edited Mar 15, 2018 at 18:40

dpst

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answered Aug 18, 2011 at 22:30

Peter

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1 Comment

Michael Kohl Over a year ago

Maybe have a look at this thread: stackoverflow.com/questions/273262/… This solution is listed there too.

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