sed and awk
Chapter 3
Understanding
Regular Expression Syntax
3.2 a line-up of characters
In addition, sed uses the backslash to cause a group of ordinary characters to be interpreted as metacharacters, as shown in below:
\( \) \{ \} \n
The n in the "\n" construct represents a digit from 1 to 9
But in awk ,we use () to group regular expressions.