在管道分隔的字段上排序不符合预期 [英] sort on pipe-delimited fields not behaving as expected

问题描述

考虑这个很小的文本文件:

Consider this tiny text file:

ab
a

如果通过sort(1)运行它，则会得到

If we run it through sort(1), we get

a
ab

因为当然a在ab之前.

但是现在考虑这个文件:

But now consider this file:

ab|c
a|c

如果通过sort -t'|'运行它，我们再次希望a在ab之前排序，但事实并非如此！ (请在您的Unix版本下试用并查看.)

If we run it through sort -t'|', we again expect a to sort before ab, but it does not! (Try it under your version of Unix and see.)

我认为这里发生的是sort的-t选项不是真正分隔字段-可能正在改变字段2的开始方式(例如)找到了，但这并没有改变字段1 结束的方式. a|c在ab|c之后排序，因为'|'在ASCII中在'b'之后. (就像-t'|'参数被忽略一样，因为没有它，您将得到相同的结果.)

What I think is happening here is that the -t option to sort is not really delimiting fields -- it may be changing the way (say) the start of field 2 would be found, but it's not changing the way field 1 ends. a|c sorts after ab|c because '|' comes after 'b' in ASCII. (It's as if the -t'|' argument is ignored, because you get the same result without it.)

那么这是sort中的错误还是我的理解?有没有办法对第一个以竖线分隔的字段进行正确排序?

So is this a bug in sort or in my understanding of it? And is there a way to sort on the first pipe-delimited field properly?

这个问题是我试图回答另一个SO问题加入声明而忽略条目的

This question came up in my attempt to answer another SO question, Join Statement omitting entries .

推荐答案

sort的默认行为是将字段1到行尾的所有内容都视为排序键.如果要首先对字段1进行排序，然后对字段2进行排序，则需要明确指定.

sort's default behavior is to treat everything from field 1 to the end of the line as the sort key. If you want it to sort on field 1 first, then field 2, you need to specify that explicitly.

$ sort -k1,1 -k2,2 -t'|' <<< $'ab|c\na|c'
a|c
ab|c

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