Shell Programming and Scripting

Hi!

I have a trouble with the sort and the uniq.
I know I have to use them, I just have trouble with putting them in the right order.

I have a text file with unsorted lines (each line has a few words, the first word in the line is a number.).

I need to sort this file in order to be able to use the uniq command.

I tried to write it like this:

Code:

 
sort -n file | uniq

(I wrote the -n option because the first string in each line is a number. Is it okay?)

but when I cat the file it's not changed, and furthermore, the output is doubling a few lines not necessarily.

What is wrong?

Thanks,
Shira.

Might need a little more info.

What are the file contents?

You also need to redirect and then overwrite the original file.

sort -n $file | uniq > $ftemp

This ~should~ give you a numerically sorted file --- with all duplicate
lines removed.

HOWEVER!!

If you're thinking of changing this:

1 ant
3 cat
2 bat
4 ant

to this:

1 ant
2 bat
3 cat

No, that won't work.

this is the "formula" of my file:

123 12 something1
234 24 something2
345 36 something3
234 24 something2

I know that if a line starts with a certain number, then all the lines that start with the same number equal to this line in all fields.

The problem is to sort it and to uniq it.

don't know, shira.

sort -n a | uniq

worked for me:

123 12 something1
234 24 something2
345 36 something3

file a contained:

123 12 something1
234 24 something2
345 36 something3
234 24 something2

maybe something more specific like:

sort -n -k1,2 a | uniq

ok, now I checked it, and the problem was that I didn't redirect the whole command into another file. So thanks.

This is what I wrote and it worked:

Code:

sort -n file | uniq > temp

Why can't I change the original file? Is there any way I can?

Most unix commands and functions relative to files require the input and output files to be different. For safety reasons, but also the issue of how to process a large file at the same time you are doing something to a file.
Typical solution is of the form

Code:

sort file1 >file1.srt
#sometimes put a verification here; just in case
mv file1.srt file1

But, beware of automatically over-writing your original file. If you start with 1000 records, but some part of your command does not quite work as you thought, then you might end up with zero records.

Code:

{ rm file; sort -nu > file;}< file