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How can I use @ARGV

digioleg54
User

Aug 24, 2016, 10:21 AM

Post #1 of 10 (4307 views)

How can I use @ARGV	Can't Post

I am trying to read arguments from command line, this way:

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

my $file = $ARGV[1];
print "$file\n";
open (FL,"<$file") or die "Could not open file $file $!\n";

while(<FL>){
print "$_";
}

My command line:

perl readfile.pl file.txt

it always show the errors:

Use of uninitialized value $file in concatenation (.) or string at readfile.pl line 7.
Use of uninitialized value $file in concatenation (.) or string at readfile.pl line 7.
Could not open file ,No such file or directory at readfile.pl line 7.

file.txt created on the same directory as my script.
Version:

This is perl 5, version 22, subversion 2 (v5.22.2) built for darwin-2level

Can somebody explain me , why?

FishMonger
Veteran / Moderator

Aug 24, 2016, 1:40 PM

Post #2 of 10 (4301 views)

Re: [digioleg54] How can I use @ARGV [In reply to]	Can't Post

Arrays are 0 indexed. The first element is at index 0 not 1.

Code

my $file = $ARGV[0];

Code

my $file = shift @ARGV;

(This post was edited by FishMonger on Aug 24, 2016, 1:41 PM)

digioleg54
User

Aug 24, 2016, 1:51 PM

Post #3 of 10 (4297 views)

Re: [FishMonger] How can I use @ARGV [In reply to]	Can't Post

I know that, 0 element is the program name, the second is file name, that is why I made it ARGV[1]. I need the file name;

FishMonger
Veteran / Moderator

Aug 24, 2016, 1:56 PM

Post #4 of 10 (4294 views)

Re: [digioleg54] How can I use @ARGV [In reply to]	Can't Post

In Reply To

I know that, 0 element is the program name, the second is file name, that is why I made it ARGV[1]. I need the file name;

WRONG

Code

c:\test>type test.pl 
#!/usr/bin/perl 
 
use strict; 
use warnings; 
use Data::Dumper; 
 
print Dumper \@ARGV;

Code

c:\test>perl test.pl file.txt 
$VAR1 = [ 
          'file.txt' 
        ];

(This post was edited by FishMonger on Aug 24, 2016, 1:56 PM)

digioleg54
User

Aug 24, 2016, 1:59 PM

Post #5 of 10 (4291 views)

Re: [FishMonger] How can I use @ARGV [In reply to]	Can't Post

I know it, unfortunately DUMPER is not working, I don't know why. Should it be installed separate from Perl version?

FishMonger
Veteran / Moderator

Aug 24, 2016, 2:00 PM

Post #6 of 10 (4290 views)

Re: [digioleg54] How can I use @ARGV [In reply to]	Can't Post

The program name is in $0 not @ARGV

FishMonger
Veteran / Moderator

Aug 24, 2016, 2:01 PM

Post #7 of 10 (4289 views)

Re: [digioleg54] How can I use @ARGV [In reply to]	Can't Post

Data::Dumper is a core module that comes with perl. If you don't have it, then your perl installation is broken.

FishMonger
Veteran / Moderator

Aug 24, 2016, 2:07 PM

Post #8 of 10 (4285 views)

Re: [digioleg54] How can I use @ARGV [In reply to]	Can't Post

Here's the example with using the Data::Dumper module.

Code

c:\test>type test.pl 
#!/usr/bin/perl 
 
use strict; 
use warnings; 
 
print "Program name is: $0\n"; 
print "The first arg passed to the script is: $ARGV[0]\n";

Code

c:\test>perl test.pl file.txt 
Program name is: test.pl 
The first arg passed to the script is: file.txt

digioleg54
User

Aug 24, 2016, 2:08 PM

Post #9 of 10 (4283 views)

Re: [FishMonger] How can I use @ARGV [In reply to]	Can't Post

Strange, now everything is working, Dumper also.
OK,
Thanks

FishMonger
Veteran / Moderator

Aug 24, 2016, 2:11 PM

Post #10 of 10 (4280 views)

Re: [digioleg54] How can I use @ARGV [In reply to]	Can't Post

It doesn't appear that you understand the minimum basics of perl. You should get a beginner level book and do some reading.

The best one available is "Learning Perl, 6th Edition"
http://shop.oreilly.com/product/0636920018452.do

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