What kind of behavior "<<<"?

Question

I get the following code to get a fingerprint from private key of OpenSSH.

$ key=`ssh-keygen -yf ~/.ssh/id_rsa`; ssh-keygen -lf /dev/stdin <<<$key

However, I do not know <<< $key syntax. What behavior is this? Is there a web site that explains this syntax?

That's a [Here String](http://www.gnu.org/software/bash/manual/bashref.html#Here-Strings). — Etan Reisner, Jul 15 '15 at 19:55
@TrisNefzger, no, `<"$key"` is reading from a file named by the expansion of `"$key"`, which is a different operation. — Charles Duffy, Jul 15 '15 at 19:56
There is a site called google. If you type "bash triple less than" it can take you to many magical places that tells you what it does... — ODelibalta, Jul 15 '15 at 19:56
It's not reasonable to have a "what is X?" question for every single language feature X. For that reason, I'm skeptical that questions of this form are worthwhile contributions to the knowledge base. — Charles Duffy, Jul 15 '15 at 19:56
@TrisNefzger, ...a man page already linked to at a more authoritative location by Etan, and quoted directly in an answer by Mike. — Charles Duffy, Jul 15 '15 at 20:03
Looking it up in http://linux.die.net/man/1/bash it says "<< — , Jul 15 '15 at 20:17

score 4 · Accepted Answer · edited Jul 15 '15 at 20:01

4

Here Strings

A variant of here documents, the format is:
  <<<word
The word is expanded and supplied to the command on its standard input.

edited Jul 15 '15 at 20:01

Charles Duffy

answered Jul 15 '15 at 19:57

MichalH

thanks, I Although Here-Document knew, I did not know the existence of the Here-String. – higr Jul 16 '15 at 05:43

1 Answers1