how review mutliline quarrel stdin non-static imitation out shell(sh,bash)?

what i wish following:

1. read churned line quarrel stdin non-static a


2. make several operations a


3. pipe a but losing delimiter black (\n,\r,\t,etc) another command

the tide problem that, i can't review read command, since stops reading during newline.

i review stdin cat, this:

my_var=`cat /dev/stdin`

, nonetheless following i don't know imitation it. newline, tab, delimiters still there.

my illustration book looks this:

#!/usr/local/bin/bash

a=`cat /dev/stdin`

if [ ${#a} -eq 0 ]; then
        exit 0
else
        cat ${a} | /usr/local/sbin/nextcommand
fi