bash "while do echo" can't function correctly

[何建军]

Hi,

I use a very simple statement "cat test.txt | while read line; do echo $line; done", 
test.txt is very small, no more than 100 lines. but the execution of the statement 
paused during process.

test.txt is pasted on http://paste.bradleygill.com/index.php?paste_id=1647399

desmond.he@xgimi-dev:/studio/desmond.he$ help | head -n 1
GNU bash, version 4.3.11(1)-release (x86_64-pc-linux-gnu)
desmond.he@xgimi-dev:/studio/desmond.he$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=14.04
DISTRIB_CODENAME=trusty
DISTRIB_DESCRIPTION="Ubuntu 14.04.3 LTS"

Thanks for help~