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.

score 13 · Accepted Answer · edited May 04 '17 at 21:03

13

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

edited May 04 '17 at 21:03

Holger Just

answered May 04 '17 at 19:24

Derek Wright

score 5 · Answer 2 · answered May 09 '20 at 03:28

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

2 Answers2