Use of uninitialized value in a Perl script - linux

Question

I have the below program for checking the file availability in a Unix directory.
my $numbera = "c://";
my $numberb = "test1.txt";
check_file_exist($numbera, $numberb);
sub check_file_exist {
my $download_filename;
my ($numbera,$numberb) = #_;
$download_filename = $numbera.$numberb;
print "*** $download_filename ****";
my $mtime = (stat $download_filename)[9];
my $filedatetime = scalar localtime $mtime;
if (-e $download_filename) {
print "Data File Exist which is created on $filedatetime";
}
unless (-e $download_filename) {
print "File not exists";
}
}
while running the program I am getting the below error:
*** data_file=HASH(0xa912f0)/home1/saravanan/ ****
Use of uninitialized value in localtime at /home1/saravanan/data_file.pl

Answer 1

First, always put these in your program:
use strict;
use warnings;
When you use strict, you will have to declare your variables with either my or our (HINT: You use my about 99.99% of the time).
These will catch all sorts of errors in your script:
Also, use indentations. It makes your script easier to read. It is also bad form to output inside of your subroutine (unless that is the purpose of your subroutine. Instead, have your subroutine return (or not return a value), and then display that.
Your problem is that you were attempting to stat a file before you knew whether it exists or not. You need to put your stat inside your if statement where you check for the file's existence.
I've made a few changes besides what I stated above:
I use say instead of print. If you use print, you have to put in a terminating \n. The say command does this for you.
I pull in my parameters as soon as I get the subroutine (and use better variable names than $numbera and $numberb.
I use if/then/else instead of doing an if and then an unless with the same test. I no longer use unless in most circumstances. It's simply clearer to say if ( not ... ).
The subroutine either returns a datestamp or returns nothing. I check for the return value of the subroutine with my if statement.
Here's your program updated a bit:
use warnings;
use strict;
use autodie;
use feature qw(say);
use Data::Dumper;
my $numbera = "/Users/david";
my $numberb = ".profile";
if ( my $timestamp = check_file_exist( $numbera, $numberb ) ) {
say "The file was downloaded at $timestamp";
}
else {
say "The file does not exist";
}
sub check_file_exist {
my $directory = shift;
my $file_name = shift;
my $download_filename = "$directory/$file_name";
my #stat = stat($download_filename);
if (not #stat) {
return;
}
my $mtime = $stat[9];
return scalar localtime $mtime;
}