Triple Less Than Sign in Bash

Question

While reading other people's bash code, I found a triple less than sign.

What does <<< mean in Bash?

Type `info bash` or read the [bash manual here](http://www.gnu.org/software/bash/manual/bash.html), and search for "<<<". You should develop the habit of Reading The Fine Manual before posting a question. — Keith Thompson, Aug 29 '13 at 15:34
It's ok to use Google: http://linux.die.net/abs-guide/x15683.html — Matt Bryant, Aug 29 '13 at 15:34
@hakre: 1. Follow the link in my previous comment. 2. Find out how to install `info` on your system. (One possible difficulty: Debian does not install the bash info manual by default. This does not apply to Debian derivatives like Ubuntu.) — Keith Thompson, Aug 29 '13 at 16:08
I think this has been downvoted because it was linked from [meta](http://meta.stackexchange.com/questions/208756/should-we-reopen-a-question-if-it-is-closed-with-a-wrong-reason). Sorry @user2675805. — user000001, Nov 25 '13 at 11:36
As always, links to the ABS should be taken with a grain of salt. The reference manual is unfortunately quite terse. — tripleee, Sep 10 '20 at 05:25

score 12 · Accepted Answer · answered Aug 29 '13 at 15:32

12

It means that the standard input of the command is set to a given string.

For example

command <<< "String"

is equivalent to

echo "String" | command

answered Aug 29 '13 at 15:32

user000001

1

what's the difference between "<<<" and "<"? Does "<<<" work on string and "<" work on file? – user2675805 Aug 30 '13 at 14:35
1

@user2675805 Exactly. – user000001 Aug 30 '13 at 14:39
1

Please note that this syntax is [not in POSIX](https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_07). – Totor Apr 29 '23 at 13:23

score 5 · Answer 2 · answered Aug 29 '13 at 15:36

It's a here string:

It's actually an enhanced Here Document:

cat <<EOF
data
here
EOF

Equivalent to:

cat <<< "data
here"

Please read more info through man bash.

2 Answers2