 | Chapter 34 The sed Stream Editor |  |
| Chapter 34 The sed Stream Editor | |
The quit command, q, causes sed to stop reading new input lines (and stop sending them to the output). Its syntax is:
[
line-address]q
| Warning! | It can take only a single-line address.
Once the line matching address (line-address) is reached, the script will be
terminated. |
|---|
For instance, the following one-liner uses the quit command to print the first ten lines from a file:
%sed '10q' myfile...
sed prints each line until it gets to line 10 and quits.
The previous version is much more efficient than its functional equivalent:
-n |
% |
|---|
(especially if myfile is a long file) because sed doesn't need to keep reading its input once the patterns in the script are satisfied.
One possible use of q is to quit a script after you've extracted what you want from a file. There is some inefficiency in continuing to scan through a large file after sed has found what it is looking for. The getmac (43.20) script uses this technique.
-
|  | |
| 34.20 The sed Test Command |  | 34.22 Dangers of the sed Quit Command |
