How to isolate a word that corresponds with a letter from a different column of a CSV file? - perl

Question

I have a CSV file, like this:
ACDB,this is a sentence
BECD,this is another sentence
BCAB,this is yet another
Each character in the first column corresponds to a word in the second column, e.g., in the first column, A corresponds with "this", C with "is", D with "a", and B, with sentence.
Given the variable character, which can be set to any of the characters appearing in the first column, I need to isolate the word which corresponds to the selected letter, e.g., if I set character="B", then the output of the above would be:
sentence
this
this another
If I set `character="C", then the output of the above would be:
is
another
is
How can I output only those words which correspond to the position of the selected letter?
The file contains many UTF-8 characters.
For every character in column 1, there is always an equal number of words in column 2.
The words in column 2 are separated by spaces.
Here is the code I have so far:
while read line
do
characters="$(echo $line | awk -F, '{print $1}')"
words="$(echo $line | awk -F, '{print $2}')"
character="B"
done < ./file.csv

Answer 1

This might work for you:
x=B # set wanted key variable
sed '
:a;s/^\([^,]\)\(.*,\)\([^ \n]*\) *\(.*\)/\2\4\n\1 \3/;ta # pair keys with values
s/,// # delete ,
s/\n[^'$x'] [^\n]*//g # delete unwanted keys/values
s/\n.//g # delete wanted keys
s/ // # delete first space
/^$/d # delete empty lines
' file
sentence
this
this another
or in awk:
awk -F, -vx=B '{i=split($1,a,"");split($2,b," ");c=s="";for(n=1;n<=i;n++)if(a[n]==x){c=c s b[n];s=" "} if(length(c))print c}' file
sentence
this
this another

Answer 2

This seems to do the trick. It reads data from within the source file using the DATA file handle, whereas you will have to obtain it from your own source. You may also have to cater for there being no word corresponding to a given letter (as for 'A' in the second data line here).
use strict;
use warnings;
my #data;
while (<DATA>) {
my ($keys, $words) = split /,/;
my #keys = split //, $keys;
my #words = split ' ', $words;
my %index;
push #{ $index{shift #keys} }, shift #words while #keys;
push #data, \%index;
}
for my $character (qw/ B C /) {
print "character = $character\n";
print join(' ', #{$_->{$character}}), "\n" for #data;
print "\n";
}
__DATA__
ACDB,this is a sentence
BECD,this is another sentence
BCAB,this is yet another
output
character = B
sentence
this
this another
character = C
is
another
is

Answer 3

Here's a mostly - done rump answer.
Since SO is not a "Do my work for me" site, you will need to fill in some trivial blanks.
sub get_index_of_char {
my ($character, $charset) = #_;
# Homework: read about index() function
#http://perldoc.perl.org/functions/index.html
}
sub split_line {
my ($line) = #_;
# Separate the line into a charset (before comma),
# and whitespace separated word list.
# You can use a regex for that
my ($charset, #words) = ($line =~ /^([^,]+),(?(\S+)\s+)+(\S+)$/g); # Not tested
return ($charset, \#words);
}
sub process_line {
my ($line, $character) = #_;
chomp($line);
my ($charset, $words) = split_line($line);
my $index = get_index_of_char($character, $charset);
print $words->[$index] . "\n"; # Could contain a off-by-one bug
}
# Here be the main loop calling process_line() for every line from input