Sign up ×
Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Ruby Version Manager (RVM) installed like so:

bash -s stable < <(curl -s

I understand what first < mean (feeds bash script to bash interpreter), I'm confused with <(...) part. So, what parentheses do here and the less than sign. In which cases we can use same syntax?

I tried to dig on the internet, found this SO question and this question on ubuntuforums: But still have no idea why we use those parentheses and why we use input redirection twice.

bash < curl -s

ain't the same?


share|improve this question

2 Answers 2

up vote 6 down vote accepted

It's process substitution. It feeds the output of the command into a FIFO that can be read from like a normal file.

share|improve this answer
got it... link to a reference is what I needed :) – Nemoden Mar 26 '12 at 5:51

It means "run the command inside the brackets, and return a filename that represents the standard output of that command here".

So, that translates to two commands:

curl ... > something
bash -s stable < something

...where "something" is the magic. (Typically, /dev/fd/... or a pipe.)

share|improve this answer
thank you! Helped to understand what is happening – Nemoden Mar 26 '12 at 5:51

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.