How to detect if a Ruby script is running through a shell pipe?

Question

My question is similar to this one: How to detect if my shell script is running through a pipe?. The difference is that the script I’m working on is written in Ruby.

Let’s say I run:

./test.rb

I expect text on stdout with color, but

./test.rb | cat

I expect the color codes to be stripped out.

Holger Just · Accepted Answer · 2017-05-04 21:03:37Z

16

Use $stdout.isatty or more idiomatically, $stdout.tty?. I created a little test.rb file to demonstrate, contents:

puts $stdout.isatty

Results:

$ ruby test.rb
true

$ ruby test.rb | cat
false

Holger Just

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answered May 4, 2017 at 19:24

Derek Wright

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1 Comment

or more idiomatic: $stdout.tty?

Kurt Stephens · Accepted Answer · 2020-05-09 03:28:25Z

6

Use IO#stat.pipe?. IO#tty? returns true only on a TTY device. Returns false for UNIX-style pipes (see "man 2 pipe").

 $ echo "something" | ruby -e 'puts $stdin.stat.pipe?'
true
 $ echo "something" | ruby -e 'puts $stdin.tty?'
false
 $ ruby -e 'puts $stdin.tty?'
true

answered May 9, 2020 at 3:28

Kurt Stephens

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