Why does read in bash need to cooperate with while to read the contents of /dev/stdin

Blog Background

In echo hello | read line; echo $line does not work but works when using while

Solution

echo "Hello, World!"| (read var1 var2; echo -e "$var1 \n$var2")

You need to enclose read and echo in parentheses and execute them in the same subshell. The specific principle is unknown.

References

https://www.6fzz.com/93620.html