Optionally allowing STDIN to be passed to a rake task

Question

I have a rake task that I would like to be optionally given stdin, e.g. either of the following could work:

rake my_task
cat foo.txt | rake my_task

The problem is that I don't have a reliable way to check whether STDIN was given to the program. Here's my current attempt, which just hangs indeterminately:

instructions = STDIN.read.split("\n") if STDIN.tty?

I added the STDIN.tty? after reading how-can-you-check-for-stdin-input-in-a-ruby-script. It is returning true when I invoke it with rake my_task (no stdin)

hope one of these http://cobwwweb.com/4-ways-to-pass-arguments-to-a-rake-task options work for you — fanta, Jun 20 '17 at 21:21
I think you just need to invert your condition, i.e. you want to read `$stdin` if it’s _not_ a tty (it’s a pipe). — matt, Jun 20 '17 at 21:35

score 0 · Accepted Answer · edited Jun 20 '17 at 23:58

0

You just need to invert the condition. What you want is to read stdin if it’s not a tty:

instructions = STDIN.read.split("\n") unless STDIN.tty?

edited Jun 20 '17 at 23:58

max pleaner

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answered Jun 20 '17 at 23:54

matt

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Edited to use unless instead of `if !` – max pleaner Jun 20 '17 at 23:58

Optionally allowing STDIN to be passed to a rake task

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