Putting a filename as a parameter to a perl script then reading from it in the code?

[Mikeyb0y]

Hi Monks, I am learning perl but come from an ICL vme background so our scl scripting is although in some ways similar the way it handles files is easy. How can i write a script that access a filename supplied by the user as the only parameter? then read each line and put the csv fields into variables. if anyone has any quick code they could let me use i would be grateful i just need to crack this and the rest should be easy i hope

[moritz]

The variable @ARGV contains the command line options. perlintro has examples for opening files and reading them line by line.

[Utilitarian]

ICL VME, >shudder<that brings back memories...
$ARGV[0] is the first paramter supplied to your script.
When you have to parse a common file format, the first response should be to search CPAN (or for a faster response, metacpan.org)for the format, there you will discover Text::CSV a module which handles all the edge cases that may arise in your data.

Welcome to Perl, you'll find it much handier to script in than scl once you get the hang of it...

[johngg]

The nice thing about Perl is that it very often does what you want without you having to jump through hoops. If you supply a file name (or multiple file names) as an argument, Perl will automatically open the file for you so you can read it using an empty <> (readline) function. The following steps create a simple CSV file and an equally simple script to read it.

$ cat > xxx.csv
Fred,male,25
Beth,female,31
Joe,male,22
$ cat > xxx
#!/usr/bin/perl
#
use strict;
use warnings;

while ( <> ) # Read the file supplied as argument
{
    chomp; # Remove line terminator
    my( $name, $sex, $age ) = split m{,};
    printf qq{Name: %s\n Sex: %s\n Age: %s\n-----\n},
       $name, $sex, $age;
}
$ chmod +x xxx
$ ./xxx xxx.csv 
Name: Fred
 Sex: male
 Age: 25
-----
Name: Beth
 Sex: female
 Age: 31
-----
Name: Joe
 Sex: male
 Age: 22
-----
$

I hope this is helpful.

[Anonymous Monk]

If you're going to use that you should remember to use ARGV::readonly;

But it this is indeed CSV, don't bother reinventing the wheel, start with Text::CSV, expecially these http://search.cpan.org/dist/Text-CSV_XS/MANIFEST programs

examples/csv2xls	Script to onvert CSV files to M$Excel
examples/csv-check	Script to check a CSV file/stream
examples/csvdiff	Script to shoff diff between sorted CSV files
examples/parser-xs.pl	Parse CSV stream, be forgiving on bad lines

[space_monk]

Please use Text::CSV or one of its friends to read your CSV file. An example of how to read a CSV file is in the CPAN documentation. Whilst you can simply split on commas as the previous example by johngg showed, it doesn't cater for quoted fields within CSV files. The most important thing to learn about Perl is not that There's More Than One Way To Do It (TMTOWTDI), it is that Someone Has Almost Certainly Done It Before, so use libraries where possible.