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Re: File Reading
by andreas1234567 (Vicar) on Oct 01, 2007 at 13:19 UTC
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Any ideas how to tackle this problem is welcome
Create a hash of arrays, where the hash keys are the elements one the first line, and the array elements are values from each column respectively. Read perldata, perlfaq4.
$ perl -w 641872.pl
$VAR1 = {
'EYES' => [
'BLUE',
'BROWN'
],
'AGE' => [
'32',
'54'
],
'HAIR' => [
'BLONDE',
'BROWN'
]
};
Update: The implementation is intentionally excluded since this is an obvious homework question. Memory concerns are considered out of scope. In real life I would probably use cut (Unix).
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Hi,
++andreas1234567, yes, that will work, but you will always fill your memory with a lot of unnecessary data before you actually output any data.
Without saying too much (to not make the OP's homework too easy ;-)), I'd first find out which column is actually searched for, then go through the rest of the file line by line and print the only column that is requested.
No building up of a huge hash...
Regards,
svenXY
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Re: File Reading
by Skeeve (Parson) on Oct 01, 2007 at 13:04 UTC
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Re: File Reading
by Limbic~Region (Chancellor) on Oct 01, 2007 at 14:36 UTC
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mantra2006,
I agree with others, this looks like homework. After reading a few of the 70+ other posts you have made over the last year, I am willing to give you the benefit of a doubt.
#!/usr/bin/perl
use strict;
use warnings;
my $file = $ARGV[0] or die "Usage: $0 <input_file>";
open(my $fh, '<', $file) or die "Unable to open '$file' for reading: $
+!";
my $header = <$file>;
chomp $header;
my @field = split /:/, $header;
print "What field would you like to look for?\n";
my $choice = <STDIN>;
chomp $choice;
while (<$fh>) {
chomp;
my %record;
@record{@field} = split /:/;
print "$record{$choice}\n";
}
It is untested and intentionally does not do a lot of the error checking that it should. These are tasks that you will need to do yourself.
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Re: File Reading
by jwkrahn (Abbot) on Oct 01, 2007 at 13:43 UTC
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$ echo "AGE:EYES:HAIR
32:BLUE:BLONDE
54:BROWN:BROWN" | \
perl -F: -lane'
BEGIN { $key = uc shift }
if ( $. == 1 ) { @x{ map uc, @F } = 0 .. $#F }
else { print $F[ $x{ $key } ] }
' age
32
54
$ echo "AGE:EYES:HAIR
32:BLUE:BLONDE
54:BROWN:BROWN" | \
perl -F: -lane'
BEGIN { $key = uc shift }
if ( $. == 1 ) { @x{ map uc, @F } = 0 .. $#F }
else { print $F[ $x{ $key } ] }
' eyes
BLUE
BROWN
$ echo "AGE:EYES:HAIR
32:BLUE:BLONDE
54:BROWN:BROWN" | \
perl -F: -lane'
BEGIN { $key = uc shift }
if ( $. == 1 ) { @x{ map uc, @F } = 0 .. $#F }
else { print $F[ $x{ $key } ] }
' hair
BLONDE
BROWN
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Hi,
++jwkrahn for reminding me of the precious $.!
Regards,
svenXY
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Re: File Reading
by zer (Deacon) on Oct 01, 2007 at 13:12 UTC
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yes i concur.
Either way this looks like it is better done with a shell script than perl just from the sounds of it. (this is where i get a ton of --'s) | [reply] |
Re: File Reading
by ambrus (Abbot) on Oct 02, 2007 at 07:30 UTC
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I recommend the $_ = <>; @f = split; while (<>) { @a{@f}= split; print $a{$field}; } trick from Re: updating Input file.
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Re: File Reading
by dwm042 (Priest) on Oct 01, 2007 at 14:57 UTC
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This is a coded solution to the issue, a mostly plain one.
#!/usr/bin/perl
use warnings;
use strict;
my $tag = shift;
die ("You need to enter a tag.\n") unless ( $tag =~ /\w+/ );
my $count = 0;
my @headers = ();
my %hash = ();
while(my $d = <DATA>) {
$count++;
chomp ($d);
if ( $count < 2 ) {
@headers = split/:/, $d;
}
else {
my @temp = split/:/, $d;
push @{$hash{$headers[$_]}}, $temp[$_] for ( 0 .. $#headers );
+
}
}
if ( defined($hash{$tag}) ) {
print "$tag = ",join( ',', @{$hash{$tag}} ), "\n";
}
else {
print "Tag $tag not found.\n";
}
__DATA__
AGE:EYES:HAIR
32:BLUE:BLONDE
54:BROWN:BROWN
And the results are:
C:\Code>perl show_tags.pl foo
Tag foo not found.
C:\Code>perl show_tags.pl AGE
AGE = 32,54
C:\Code>perl show_tags.pl EYES
EYES = BLUE,BROWN
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Re: File Reading
by aquarium (Curate) on Oct 01, 2007 at 15:20 UTC
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aquarium was closest. mantra2006 was trying to get a job.
he was unsuccessful.
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So now as he was unseccessfull, I'd like to get the job ;-)
Here is my solution, lacking any kind of error checking of course...
#!/usr/bin/perl
use strict;
use warnings;
# read headline
$_= <DATA>;
chomp;
# split into words
my @headline= split /:/;
# assign each word a column number
my %headline;
@headline{@headline}= (0..$#headline);
# get the required columns
my @columns= @headline{@ARGV};
# print the column headers
print join(':',@ARGV),"\n";
# read each line
while (<DATA>) {
chomp;
# and print what's requested
print join(':',(split /:/)[@columns]),"\n";
}
__DATA__
AGE:EYES:HAIR
32:BLUE:BLONDE
54:BROWN:BROWN
s$$([},&%#}/&/]+}%&{})*;#$&&s&&$^X.($'^"%]=\&(|?*{%
+.+=%;.#_}\&"^"-+%*).}%:##%}={~=~:.")&e&&s""`$''`"e
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