34.22. 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: [line-address]q 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 Section 34.3 % sed -n '1,10p' myfile (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. -- TOR Copyright © 2003 O'Reilly & Associates. All rights reserved. |
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