Bash here document produces no output, any idea why?

问题

On my Acer 725 with Lubuntu 13.04 this little script:

#!/bin/bash

echo "======"
echo <<xxxxx
aaaaaaaaaqqqqqqqqq
xxxxx
echo "======"

produces this output:

======

======

It should produce this:

======
aaaaaaaaaqqqqqqqqq
======

I've searched all over for a reason but I can't find anything. I have a horrible feeling that I am missing something embarrassingly obvious.

Any ideas?

回答1:

I have a horrible feeling that I am missing something embarrassingly obvious.

Use cat instead of echo:

cat <<xxxxx
aaaaaaaaaqqqqqqqqq
xxxxx

回答2:

Heredocs send the content to stdin. echo doesn't read from stdin.

来源：https://stackoverflow.com/questions/21091826/bash-here-document-produces-no-output-any-idea-why