Perl. how to open csv file, count how many rows and columns it has

Question

I have a msft.csv file. Columns are separated by ",". which is actually a table. Can't post a picture, don't understand how to attach the file.

My task is:

Open the file and count and print how many rows and columns it has. Columns are separated by ",".
Open the file and print maximum, minimum for these columns: Open,High,Low,Close,Volume,Adj Close with the corresponding date
Open the file and calculate and print average for these columns: Open,High,Low,Close,Volume,Adj Close

I have read some literature but I can't do anything useful. Actually all I was able to do is open the file and print it out.

I figured I should use Text::CSV module, but I can't figure the right syntax.

I worked through first 6 chapters here http://www.perl.org/books/beginning-perl/ I've also read some info on http://perldoc.perl.org/index.html
but so far I'm a zero.

If it's possible - it would be great to see the solution with/without using module. I'll try to figure what you've done there, but if it's not too much trouble, I'll appreciate if you can explain at least something.

Any advice on what literature I should read? Any useful links?

p.s English is my second language, so please forgive me my grammar.

p.p.s I can do smtg with text files, but I haven't seen a single table example.

i tried using module. i tried using split. its just i cant find proper example, and cant get the syntax right. im stuck on the first tast- counting rows and columns. #!/usr/bin/perl use strict; use warnings; open FH, "msft.csv" or die $!; my @array = <FH>; my $scalar = @array; print "file has $scalar rows\n"; exit; the only way im able to get rows. how to split it into columns and count it? the file Date Open High Low Close Volume Adj Close 8/6/2013 31.55 31.67 31.38 31.58 36331500 31.58 — AndreiMotinga
– AndreiMotinga, Commented Aug 13, 2013 at 23:00

ptierno · Accepted Answer · 2013-08-13 22:58:44Z

2

Something like this should work for you:

#!/usr/bin/perl
use strict;
use warnings;

my $filename = 'test.txt';
my $line;
my $lines = 0;
my @columns;

open(my $fh, '<', $filename) or die "Can't open $filename: $!";

$line = <$fh>;
@columns = split(',', $line);
$lines++ while <$fh>;
close $fh;

print "$lines lines\n";
print scalar @columns . " columns\n";

answered Aug 13, 2013 at 22:58

ptierno

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8 Comments

AndreiMotinga Over a year ago

awesome - it worked. it produces the right output. 150 lines. 7 columns. now ill try to figure the process. Thank you.

Jonathan Leffler Over a year ago

This works for the simple cases where there are no embedded commas inside the field values. If you have to deal with that, the field will be enclosed in double quotes. At that point, you need Text::CSV or a similar module to handle the quoting correctly.

AndreiMotinga Over a year ago

can you explain to me why do we use $line? why $line = <$fh>; produces the top line, but not the whole file. and is there a difference between $fh and FH

ptierno Over a year ago

$fh is just what i named the file handle. you can use what you want. FILE, FH. Both will work. As for why <$fh> only produces one line is because perl's builtin input record seperator defaults to one new line. perlmonks.org/?node_id=287647

AndreiMotinga Over a year ago

why do we use $line $line = $fh and than columns= split (',', $line) columns = split(',', <FH>) columns = split(',', <$fh>) columns = split(',', $fh) dont work.

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