[NTLUG:Discuss] sed awk question

[David Stanaway]

On Mon, 2002-08-12 at 11:34, Chris Cox wrote:
> Bobby Wrenn wrote:
> 
> >My reading led me to believe that awk was best for working with fields rather 
> >than whole lines.
> >
> >My question last week made me think perl was better than either and more 
> >versatile than either.
> >
> Usually true.  The case where perl won't be better is cases where
> you cannot be sure of Perl's availability... which is becoming quite
> a small list btw.  As more an more Unix vendors start shipping perl
> as a standard part of their base OS install, there will be less and
> less reasons to use things like sed and awk.  Might still be
> some cases where memory and space are involved though.... or for
> old folks like myself that think naturally in terms of sed and
> awk.  Since perl is evolving (esp. v6)... I'll probably defer
> on doing much perl.  The radical changes to perl REs, while
> certainly techncially better, is a headache and a half.
> 
> >
> >
> >So, here is my question this week. I need to sort a comma delimited file and 
> >return only those line where the first field is unique. Currently I am 
> >pulling the file into Access and elimating duplicates there. There has to be 
> >a better way.
> >
> Not as easy as some would like to think...
> (this actually eliminates duplicates... technically you asked for data that
> ONLY had unique entries.... that could be done too)  Outputs the first
> occurence of the duplicate key lines when duplicates are found.
> 
> sort -t, -k1 csg.data | awk -F, '
> {
>         if ($1 != lastsaved) {
>                 print;
>                 lastsaved=$1;
>         }
> }'
> 
> The uniq program does not provide the flexibility to deal with field
> delimited files.
> 


Sorry, but that is incorrect:

dstanawa at ciderbox:~$ cat test.txt
aa,wrong,dsdf
asd,333,rewse
cc,wrong,sdsd
aa,f00f,tt
afg,sdf,sdaf
cc,dws,44
dstanawa at ciderbox:~$ sort -t, -k1 test.txt |uniq -t, -W1
aa,f00f,tt
afg,sdf,sdaf
asd,333,rewse
cc,dws,44

The problem is picking which entry gets printed, here, the file is
lexographically sorted.
 
-- 
David Stanaway
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