How to read mutliline input from stdin into variable and how to print one out in shell(sh,bash)?

Question

What I want to do is the following:

1. read in multiple line input from stdin into variable A
2. make various operations on

Answer 1

Yes it works for me too. Thanks.

myvar=`cat`

is the same as

myvar=`cat /dev/stdin`

Well yes. From the bash man page:

Enclosing characters in double quotes preserves the literal value of all characters within the quotes, with the exception of $, `, \, and, when history expansion is enabled, !. The characters $ and ` retain their special meaning within double quotes.