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Why is sort not working properly here ?

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Top Forums Shell Programming and Scripting Why is sort not working properly here ?
# 1  
Old 03-11-2013
Why is sort not working properly here ?
Platform: RHEL 5.4
In the below text file I have strings like following.

Code:
$ cat /tmp/mytextfile.txt
DISK1
DISK10
DISK101
DISK102
DISK103
DISK104
DISK105
DISK106
DISK107
DISK108
DISK109
DISK110
DISK111
DISK112
DISK113
DISK114
DISK115
.
.
.
<output snipped for better readability>
.
.
DISK459
DISK46
DISK460
DISK461
DISK462
DISK47
DISK48
DISK49
DISK5
DISK50
DISK51
DISK52
DISK53
DISK54
DISK55
DISK56
DISK57
DISK58
DISK6
DISK7
DISK8
DISK9

I wanted to sort the output based on the number after the 'DISK' string. My expected output :
Code:
 
DISK1
DISK2
DISK3
DISK4
DISK5

But when I use sort, the output looks like below


Code:
 
$ sort /tmp/mytextfile.txt
DISK1
DISK10
DISK101
DISK102
DISK103
DISK104
DISK105
DISK106
DISK107
DISK108
DISK109
DISK110
.
.
.
<output snipped for better readability>

# Trying with -n option. But , still the same output as above.
Code:
 
$ sort -n /tmp/mytextfile.txt
DISK1
DISK10
DISK101
DISK102
DISK103
DISK104
DISK105
DISK106
DISK107
DISK108
DISK109
DISK110

How can I get the expected output using sort or any other utility ?
# 2  
Old 03-11-2013
Use:
Code:
# sort -n -k 1.5 /tmp/mytextfile.txt

This User Gave Thanks to Klashxx For This Post:
kraljic
# 3  
Old 03-11-2013
Thank you. It works !! But how does this work?
What is 1.5 ?

This is what sort's man page says about -k
Code:
 
-k, --key=POS1[,POS2]
              start a key at POS1, end it at POS2 (origin 1)

Couldn't understand how -k option works from the man page's explanation.

---------- Post updated at 10:50 AM ---------- Previous update was at 08:56 AM ----------

anyone ?
# 4  
Old 03-11-2013
Do not bump up posts.

If someone doesn't answer your post immediately, wait! We are not on call.

-k tells it what column and what characters of each column to sort on. There's more detail about what denotes a column below since it's actually a bit complicated.

What does most of the work here, I think, is -n, "numeric sort".
# 5  
Old 03-11-2013
See the man page, roughly 35 lines down from your citation:
Quote:
POS is F[.C][OPTS], where F is the field number and C the character position in the field; both are origin 1. If neither -t nor -b
is in effect, characters in a field are counted from the beginning of the preceding whitespace. OPTS is one or more single-letter
ordering options, which override global ordering options for that key. If no key is given, use the entire line as the key.
# 6  
Old 03-11-2013
Since DISK is a constant four, you want to key your sort on the first field character 5 and following, numeric ordering. In the the ol day, this was '-n +0.4 -0.99' but now it is -k1.5,1.99n, as field and character offsets in +- ar zero based and in -k, one based.

If you rename your volumes with leading zeros then there is no problem with simple sort.
This User Gave Thanks to DGPickett For This Post:
hanson44
# 7  
Old 03-11-2013
Yes, you save a lot of trouble if just rename with leading zeroes. Of course, might start with DISK001 and oops now we need a DISK1000, so need to put in enough capacity.
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