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. |
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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 |
%
|
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(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.
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