A CSV file with commas in the data is particularly hard to sort, even for the unix sort, e.g.:
Luckily, or sadly, many data sets are embedded-comma-free, lulling the unwary into forgetfulness ! Early versions of MS Access had this problem, forcing me to use tab or pipe (|) separated text.
Folks,
I have a bit of an issue trying to obtain some data from a csv file using PERL. I can sort the file and remove any duplicates leaving only 4 or 5 rows containing data. My problem is that the data contained in the original file contains a lot more columns and when I try ro run this script... (13 Replies)
Hi,
I have a .csv file which contains script names, subjects and email_addresses
The first two colums are always script name and subject, the next 20 colums are email address..
What i want to do is sort the email address in alphabetical order for each row and there's around 1200 rows.
So... (3 Replies)
Hi all,
in my csv file it'll look like this, and of course it may have more columns
US to UK;abc-hq-jcl;multimedia
UK to CN;def-ny-jkl;standard
DE to DM;abc-ab-klm;critical
FD to YM;la-yr-tym;standard
HY to MC;la-yr-ytm;multimedia
GT to KJ;def-ny-jrt;critical
I would like to group... (4 Replies)
Hi,
Please help me to solve sorting in CSV file.
I have 25 columns in my CSV. (Delimiter is ",")
Summary columns are from 10 to 13 which are should not be sorted. From 1-9 and 14-25 should be able to sort in ascending. how should i do this using Sort command in unix.
If no simple commands pls... (0 Replies)
Hi everyone,
i am new to perl programming, i have a problem in extracting single column from csv file. the column is the 20th column,
please help me..
at present i use this code
#!C:/perl/bin
use warnings;
use strict;
my $file1 = $ARGV;
open FILE1, "<$file1"
or die "Can't... (13 Replies)
Hi,
I have a CSV file in following manner:
server1,env1,patch1
server1,env1,patch2
server1,env1,patch3
server1,env2,patch1
server1,env2,patch3
server2,env3,patch1
server2,env3,patch5
server2,env4,patch1
server3,env6,patch1
server3,env7,patch2
server3,env7,patch3
I want to... (6 Replies)
Hello all, I am new here and *relatively* new to Unix. I have a bit of an emergency. I have a three column file that I need to sort:
sample name, miRNA, reads per million (RPM)
There are multiple samples, and for each sample name there are multiple miRNAs and associated RPMs. Some of these... (6 Replies)
Hello!
So ive been presented with this comma-delimited file:
I need a print to look as below
"
lastname, phone_number, zip
for every person with a last name starting with the letter H, I
only with a 650-area code phone number. output should be sorted by reverse ZIP code "
I only have... (5 Replies)
I have absolutaly no idea how to get this script to sort the info in Birthdays.csv by date of birth. I know the sort -n command, however i wish to sort the file birthdays.csv by DOB. How would i go about doing this?
The below script gets user info and date of birth and then puts these info a... (3 Replies)
we have a CSV which i need to convert to XML using Perl or Unix shell scripting.
I was able to build this XML in oracle database. However, SQL/XML query is running for long time. Hence, I'm considering to write a Perl or shell script to generate this XML file. Basically need to build this XML... (3 Replies)
Discussion started by: laknar
3 Replies
LEARN ABOUT DEBIAN
sort
sort(3perl) Perl Programmers Reference Guide sort(3perl)NAME
sort - perl pragma to control sort() behaviour
SYNOPSIS
use sort 'stable'; # guarantee stability
use sort '_quicksort'; # use a quicksort algorithm
use sort '_mergesort'; # use a mergesort algorithm
use sort 'defaults'; # revert to default behavior
no sort 'stable'; # stability not important
use sort '_qsort'; # alias for quicksort
my $current;
BEGIN {
$current = sort::current(); # identify prevailing algorithm
}
DESCRIPTION
With the "sort" pragma you can control the behaviour of the builtin "sort()" function.
In Perl versions 5.6 and earlier the quicksort algorithm was used to implement "sort()", but in Perl 5.8 a mergesort algorithm was also
made available, mainly to guarantee worst case O(N log N) behaviour: the worst case of quicksort is O(N**2). In Perl 5.8 and later,
quicksort defends against quadratic behaviour by shuffling large arrays before sorting.
A stable sort means that for records that compare equal, the original input ordering is preserved. Mergesort is stable, quicksort is not.
Stability will matter only if elements that compare equal can be distinguished in some other way. That means that simple numerical and
lexical sorts do not profit from stability, since equal elements are indistinguishable. However, with a comparison such as
{ substr($a, 0, 3) cmp substr($b, 0, 3) }
stability might matter because elements that compare equal on the first 3 characters may be distinguished based on subsequent characters.
In Perl 5.8 and later, quicksort can be stabilized, but doing so will add overhead, so it should only be done if it matters.
The best algorithm depends on many things. On average, mergesort does fewer comparisons than quicksort, so it may be better when
complicated comparison routines are used. Mergesort also takes advantage of pre-existing order, so it would be favored for using "sort()"
to merge several sorted arrays. On the other hand, quicksort is often faster for small arrays, and on arrays of a few distinct values,
repeated many times. You can force the choice of algorithm with this pragma, but this feels heavy-handed, so the subpragmas beginning with
a "_" may not persist beyond Perl 5.8. The default algorithm is mergesort, which will be stable even if you do not explicitly demand it.
But the stability of the default sort is a side-effect that could change in later versions. If stability is important, be sure to say so
with a
use sort 'stable';
The "no sort" pragma doesn't forbid what follows, it just leaves the choice open. Thus, after
no sort qw(_mergesort stable);
a mergesort, which happens to be stable, will be employed anyway. Note that
no sort "_quicksort";
no sort "_mergesort";
have exactly the same effect, leaving the choice of sort algorithm open.
CAVEATS
As of Perl 5.10, this pragma is lexically scoped and takes effect at compile time. In earlier versions its effect was global and took
effect at run-time; the documentation suggested using "eval()" to change the behaviour:
{ eval 'use sort qw(defaults _quicksort)'; # force quicksort
eval 'no sort "stable"'; # stability not wanted
print sort::current . "
";
@a = sort @b;
eval 'use sort "defaults"'; # clean up, for others
}
{ eval 'use sort qw(defaults stable)'; # force stability
print sort::current . "
";
@c = sort @d;
eval 'use sort "defaults"'; # clean up, for others
}
Such code no longer has the desired effect, for two reasons. Firstly, the use of "eval()" means that the sorting algorithm is not changed
until runtime, by which time it's too late to have any effect. Secondly, "sort::current" is also called at run-time, when in fact the
compile-time value of "sort::current" is the one that matters.
So now this code would be written:
{ use sort qw(defaults _quicksort); # force quicksort
no sort "stable"; # stability not wanted
my $current;
BEGIN { $current = print sort::current; }
print "$current
";
@a = sort @b;
# Pragmas go out of scope at the end of the block
}
{ use sort qw(defaults stable); # force stability
my $current;
BEGIN { $current = print sort::current; }
print "$current
";
@c = sort @d;
}
perl v5.14.2 2010-12-30 sort(3perl)