shell sort命令-k POS1，POS2无效

Question

我使用-k选项测试了sort命令，但是我发现从POS1到POS2的sort -k POS1 [，POS2]无效

$ cat words.txt 
1 1
2 2
2 1
$ sort -k 1 words.txt 
1 1
2 1
2 2
$ sort -k 1,1 words.txt 
1 1
2 1
2 2

我认为“ sort -k 1,1 words.txt”应该返回结果为“ cat words.txt”，因为sort仅使用第一列，如果第一列相同，则默认打印顺序。

Answer 1

假设您使用的是GNU sort，则需要指定选项-s进行稳定排序。

$ sort --version
sort (GNU coreutils) 8.28
Copyright (C) 2017 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by Mike Haertel and Paul Eggert.

$ sort -k 1,1 words.txt
1 1
2 1
2 2

$ sort -k 1,1 -s words.txt
1 1
2 2
2 1

有关详细信息，请参见sort实用程序的手册页。