Delete the line

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

#!/usr/bin/perl
open FH,'test.tsv';
@data=<FH>;
$len=scalar (@data);
for($i=1;$i<=$len;$i++){
print $data[$i];
}
[download]

I have to check whether all the values from 3rd column is 0 or not. If all the values are zero, then delete the line.

id      date    name1   name2     namen
123     2010-02-23      0       0.00    0
1234    2010-02-24      0       3    0
[download]

i.e from name1. if in a file all the values are zero then I should delete the entire file. from the above example, the output file should have the row:

id      date    name1   name2     namen
1234    2010-02-24      0       3    0
[download]

Comment on Delete the line Select or Download Code

Replies are listed 'Best First'.
Re: Delete the line by Utilitarian (Vicar) on Jul 21, 2010 at 09:55 UTC
I suspect you are new to Perl, the comments in the code below are intended to be educational. I have used a couple of things you may not have seen before, `@array[2..$#array]` is a slice of an array, it can be thought of as a sub array starting at index 2 and going to the last element of the array `$#array is the last index of @array` Ok, so you have the individual records in the @data array. You now need to split the records and check that any of the values in the resultant array with an index > 2 are not equal to zero. If there are print the line. something like the following is what you are looking for. use strict; # These two lines use warnings;# will save you grief open (my $data_file, "<", 'test.tsv'); # better to use 3 argument ver +sion of open and to have a lexical filehandle my @data = <$data_file>; # scope your variables close( $data_file); # It's only polite to close up after yourself print $data[0]; # headers for my $line (@data[1..$#data]){ # More perlish not to use indices dir +ectly my @line = split(/\t/, $line); # split the values into an array print $line if (check_for_zero(@line)); # Use a routine to evaluate + the elements } sub check_for_zero{ # declare routine my @line = @_; # get the array we're called with for my $field (@line[2..$#line]){ # again more perlish return 1 if $field != 0; # We have a non-zero value } return 0; #if we got here we never met a non-zero value } [download] `print "Good ",qw(night morning afternoon evening)[(localtime)[2]/6]," fellow monks."`	[reply] [d/l] [select]
Re: Delete the line by Anonymous Monk on Jul 21, 2010 at 09:30 UTC
See Text::xSV and the many examples	[reply]
A reply falls below the community's threshold of quality. You may see it by logging in.
Re: Delete the line by Ratazong (Monsignor) on Jul 21, 2010 at 09:41 UTC
Sounds you have to enhance your code by the following logic in your loop, split your `$data[$i]` into an array containing words write the line to a new array if not all of the columns 2, 3 and 4 are zero after your `for`-loop, delete the file if the new array contains entries, write them to the file (you actually recreate the file that way) HTH, Rata	[reply] [d/l] [select]
Re: Delete the line by moritz (Cardinal) on Jul 21, 2010 at 09:40 UTC
Obviously you'll need to split the line to get to its fields, and then do a comparison, and only print if the comparison is successful. See perlintro.	[reply]
Re: Delete the line by jethro (Monsignor) on Jul 21, 2010 at 09:41 UTC
Your example is wrong, you seem to have looked at name2 for the elimination decision. For the printing you might take a look at Text::Table which will output your table nicely formatted	[reply]
Re: Delete the line by matrixmadhan (Beadle) on Jul 22, 2010 at 03:12 UTC
I know it's not in perl, trying out an awk variant here `awk '{ yes=0; for ( i=3; i<=NF; i++) { if ( $i == 0 ) { yes=1; break} +} if ( yes != 1 ) { print } }' filename` [download]	[reply] [d/l]
Re: Delete the line by JavaFan (Canon) on Jul 23, 2010 at 16:01 UTC
Don't use Perl. use `grep`: `grep -v '^[^ ][^ ]* [^ ] [.0 ]*$' input > output` [download] This assumes columns are separated by one or more spaces. And that the columns don't contain values like `.0.` or `0...0` (and that you want to keep such lines).	[reply] [d/l] [select]