我有10国集团的文献。 我想从档案中删除第18888条。
我使用的是:
sed -i 188888d file
问题确实是缓慢的。 我的理解是,这是因为档案的篇幅,但无论如何,我可以更快地这样做。
增 编
Try
sed -i 188888{;d;q;} file
You may need to experiment with which of the above semi-colons you keep, {d;q} ... being the 2nd thing to try.
这将在删除一条线后停止查找档案,但你仍然不得不花时间重写档案。 还值得测试。
sed 188888{;q;d;} file > /path/to/alternate/mountpoint/newFile
候补顶点在单独的磁盘上。
final edit Ah, one other option would be to edit the file while it is being written through a pipe
yourLogFileProducingProgram | sed -i 188888d > logFile
但是,这假设你知道你想要删除的数据总是符合第1888888条,这是可能的吗?
我希望这一帮助。
The file lines are determined by counting the character, if the line size are variable then you cannot calculate the offset to the location given a line but have to count the number of newlines.
这永远是O(n),在档案中是 n的数量。
平行算法也无助于,因为这种操作是软盘内分光仪有限,分立和组装会更慢。
如果你将在同一档案中做大量的工作,那么就有办法预先处理档案,使之更快。
A easy way is to build a index with
line#:offset
当你想找到一条线时,就你想要的线数而言,进行双轨搜索(Log n),并利用被抵消的线在原始档案中查找。
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