为什么`sort`、`sort k 1`、`sort k 1,1`的输出相等？

Question

我有一个文件：

$ cat file
1 c
8 a
1 b
5 f

我认为sort开头的命令比较所有行的第一个字段并对它们进行排序，然后对于这些行具有相同的第一个字段，然后再次开始对第二个字段进行排序，如下所示：

$sort file
1 b
1 c
5 f
8 a

我读到了选项k 1和k 1,1:之间的区别：k 1排序键可能会继续到行尾，但k 1,1它应该只对第一个字段进行排序而不考虑其他字段，但是：

$sort -k 1 file
1 b
1 c
5 f
8 a

$sort -k 1,1 file
1 b
1 c
5 f
8 a

为什么的输出sort= sort k 1=sort k 1,1等于？

我认为输出sort k 1,1 file应该是

1 c 
1 b
5 f
8 a

如果不正确，请告诉我我的错误是什么，我怎样才能得到这样的输出？

Answer 1

从 info sort

   Many options affect how ‘sort’ compares lines; if the results are
unexpected, try the ‘--debug’ option to see what happened.  A pair of
lines is compared as follows: ‘sort’ compares each pair of fields, in
the order specified on the command line, according to the associated
ordering options, until a difference is found or no fields are left.  If
no key fields are specified, ‘sort’ uses a default key of the entire
line.  Finally, as a last resort when all keys compare equal, ‘sort’
compares entire lines as if no ordering options other than ‘--reverse’
(‘-r’) were specified.  The ‘--stable’ (‘-s’) option disables this
“last-resort comparison” so that lines in which all fields compare equal
are left in their original relative order.  The ‘--unique’ (‘-u’) option
also disables the last-resort comparison.

所以为了达到你想要的结果（记住你的第一个字段是数字）

$ sort -s -k1,1n file
1 c
1 b
5 f
8 a