bug#6393: The meaning of --key of sort command?
Hi, I don't think that I completely understand what key means. In the following example, I thought that --key=2 should order the lines by the 2nd letter in each line without reordering the lines with the same 2nd letter. But it turns out my understanding is not correct. For example, u a was before a a sorting, but u a is after a a after sorting. According to the man page, I'd think the sorting is based on the 2nd column only but the 1st column. Why the 1st column matters in this case? -k, --key=POS1[,POS2] start a key at POS1 (origin 1), end it at POS2 (default end of line) $ cat input.txt u a c c a a e e p a m e a a l e a a $ sort --key=2 input.txt a a a a a a p a u a c c e e l e m e -- Regards, Peng
bug#6393: The meaning of --key of sort command?
On Thu, Jun 10, 2010 at 11:39 AM, Peng Yu pengyu...@gmail.com wrote: Hi, I don't think that I completely understand what key means. In the following example, I thought that --key=2 should order the lines by the 2nd letter in each line without reordering the lines with the same 2nd letter. But it turns out my understanding is not correct. For example, u a was before a a sorting, but u a is after a a after sorting. According to the man page, I'd think the sorting is based on the 2nd column only but the 1st column. Why the 1st column matters in this case? -k, --key=POS1[,POS2] start a key at POS1 (origin 1), end it at POS2 (default end of line) $ cat input.txt u a c c a a e e p a m e a a l e a a $ sort --key=2 input.txt a a a a a a p a u a c c e e l e m e I forget to mention the following command gives me the same thing (sorting on the 2nd fieled then the 1st field). But according to info sort, it should not the case. Example: To sort on the second field, use `--key=2,2' (`-k 2,2'). See below for more examples. $ sort --key=2,2 input.txt a a a a a a p a u a c c e e l e m e -- Regards, Peng
bug#6393: The meaning of --key of sort command?
On 06/10/2010 10:39 AM, Peng Yu wrote: Hi, I don't think that I completely understand what key means. In the following example, I thought that --key=2 should order the lines by the 2nd letter in each line without reordering the lines with the same 2nd letter. But it turns out my understanding is not correct. For example, u a was before a a sorting, but u a is after a a after sorting. '--key=2' implies a primary sort key from the second field (not second letter), through the end of the line, with a secondary sort key of the entire line. '--key=2,2' implies a primary sort key of just the second field, with a secondary sort key of the entire line. You want '--key=2,2 --stable', which disables the secondary sort over the entire line. -- Eric Blake ebl...@redhat.com+1-801-349-2682 Libvirt virtualization library http://libvirt.org signature.asc Description: OpenPGP digital signature
