shell read line
cat >b <<EOF line1 line2 line3 EOF
# 方法1 while read line do echo ${line} done < <(cat b)
# 方法2 cat b|while read line do echo ${line} done
# 方法3 while read line do echo ${line} done < b
cat >b <<EOF line1 line2 line3 EOF
# 方法1 while read line do echo ${line} done < <(cat b)
# 方法2 cat b|while read line do echo ${line} done
# 方法3 while read line do echo ${line} done < b