34.21 Uses of the sed Quit CommandThe quit command, q , causes sed to stop reading new input lines (and stop sending them to the output). Its syntax is:
For instance, the following one-liner uses the quit command to print the first ten lines from a file:
% sed prints each line until it gets to line 10 and quits. The previous version is much more efficient than its functional equivalent:
(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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