i don't understand the "sort" command


 
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# 1  
Old 03-14-2002
i don't understand the "sort" command

i have been trying to understand this chapter titled "Searching for Files and Text" for a few weeks now.

unfortunately, this chapter is one of those things, that no matter how hard you try and how long you try for, you are incapable of understanding (at least in my case)

this entire chapter, grep and it's derivatives and the sort command have been extremely frustrating.

i am hung up on the sort command more so than the others, but there are certain features that are especially difficult to understand.

this is what the book says about the sort command:

sort -options filenames(s)

the following two options are killing me:

-n performs a numeric sort.
(+|-)n begins (+n) or ends (-n) the sort with the field following the n
field

consider the following two examples, that have 8 columns (do columns=fields ?):

sort -rn +4 list -o num.list
sort -rn -3 list -o num2.list
sort +5n list -o update.list

first i would like some clarification with the (+|-)n option.

in the first example, the +4 says that we start counting from the 5th field (5th field because we start counting from 0, not 1 right?)... so when we count, we use fields 5,6,7 right?

in the second example, the -3 says we start counting from the 4th field backwards right? so 3,2,1,0?

next, i'm confused with what I see with the first two examples and the last. I notice that in the first two examples the +/- numbers (+4 and -3) are isolated options, but in the last example, +5n, the two options I mentioned earlier are combined. I don't understand why this is done, or what it means. shouldn't it be +5 -n instead of +5n? is +5 -n different from +5n?

can anyone please help reduce my confusion with this command?
# 2  
Old 03-15-2002
I would look for a different place for documentation, like
here:

sort:

http://www.mcsr.olemiss.edu/cgi-bin/...rt&max_hits=20

grep:

http://www.mcsr.olemiss.edu/cgi-bin/...ep&max_hits=20

main site:

http://www.mcsr.olemiss.edu/unixhelp/

Good Luck
# 3  
Old 03-15-2002
xyyz, don't feel too bad. The sort command still give me fits too. I typically need to fiddle with my sort option until I get what I want.

#1freebsddude, that was an awesome link on the sort command! But is only showing the original syntax. Posix has defined a new syntax using the -k option. It's probably time to switch to the newer syntax. Still once you get the old syntax, switching to the newer syntax is easy, so that link is still very good.

That link didn't answer -n question though. If you are specifying the fields, you would probably just add the n to field spec. -n mostly makes sense when use it alone. Here is a command that I need to type several times a week...

du -sk * | sort -n
 
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