http://www.perlmonks.org?node_id=1039777

torres09 has asked for the wisdom of the Perl Monks concerning the following question:

hey

I have a small issue that I have written a code where I have predefined my file , but now I want that the file should be entered by the user . So this is my code 

  my $file="Working_On.csv";            
    open(FILE,"<","$file");           
    my @lines=<FILE>;

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so what I am doing is converting that csv file to an array . please tell me a way so that Working_On.csv should be entered by the user

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Re: user input file
by kennethk (Abbot) on Jun 19, 2013 at 13:36 UTC
    The correct method for taking command line parameters into a Perl script is to use the @ARGV array. Your example might look like 
        open(FILE,"<", $ARGV[0]) or die "Open failed for $ARGV[0]: $!";   
+        
    my @lines=<FILE>;

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    which the user would invoke as 
    $ perl script.pl Working_On.csv

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    Note as well that I've added a test to see if the file open succeeded, and added a diagnostic in case it didn't. See Simple Opens in perlopentut.

    #11929 First ask yourself `How would I do this without a computer?' Then have the computer do it the same way.

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      I am working on windows , not unix so there will be no invocation . I tried your way but it does not work , may be because of OS

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        If you drag a csv file on to the script, it can be configured to read the file name from @ARGV. How are you planning to have the user invoke it?

        --MidLifeXis

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Re: user input file
by 2teez (Vicar) on Jun 19, 2013 at 15:38 UTC

    Hi torres09,
    please tell me a way so that Working_On.csv should be entered by the user

    If what you want is the user responding to "somewhat" like a prompt. The you can do like thus: 

    use warnings;
use strict;

my $file;

#create an inifite loop
while (1) {

    # ask the user for filename
    print "Enter filename > ";
    chomp( $file = <STDIN> );

    # Exit the loop, if the
    # filename exists and it's a file
    # else redo
    if ( -e $file && -f _ ) {  #Note HERE
        last;
    }
    else { redo }
}

open my $fh, '<', $file or die "can't open file: $!";
...

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    Or you check in CPAN for module that does exactly that.
    For the file test on the file entered by the user you can check this for more.

    Update: Note: If you use Perl 5.9.1 or better, you could actually write: if ( -e -f $file ) { ..
    If you tell me, I'll forget.
    If you show me, I'll remember.
    if you involve me, I'll understand.
    --- Author unknown to me
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Re: user input file
by kcott (Archbishop) on Jun 19, 2013 at 14:15 UTC

    G'day torres09,

    Update: Having posted this, I now see (from Re^4: user input file) that you only want users to enter the filename, not the data. Your OP asked about "file", not "filename" and "my @lines=<FILE>;" (in your posted code) suggested you were interested in data — you can ignore the remainder of my response (which is now hidden within <spoiler> tags).

    <Reveal this spoiler or all in this thread>

    -- Ken

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