Hi
I am stuck trying to debug a small piece of code.
This code grabs an image from an IP camera on my home network, timestamps the filename and then should save it to a file.
No matter what I do, I can't get past the uninitialised value error reported in the debug output below.

The most obvious bug would be that $snapshot->grab; is empty.
I have cut/pasted the URL from the code into my browser to make sure that the URL is correct and that I get an image. So I am reasonably confident that Grab is getting a valid image. As far as I can tell, $snapshot should hold a valid image but I don't know how to test the contents of $snapshot->grab; without first saving it to a file.
This code is running on a headless PC that I ssh into.
Google hasn't helped solve this problem. 

my $snapshot = new Image::Grab;
$snapshot->ua->timeout(5);           # define the timeout for grabbing
+ an image.  Default is 180 sec$
$snapshot-> url( "IPCamera{$key}");  #define the source of the image
$snapshot->grab;      #grab an image

mark_blob(my $pic);
$pic = $snapshot->image;  #debug

my $SaveFile = join("","$ImagePath{$key}",&timestamp,"\-snapshot\-$key
+.jpg");
print ("Save filename: $SaveFile");

open(my $fh, ">$SaveFile") || die "$SaveFile: $!";
binmode $fh;  # for MSDOS derivations.
print $fh $pic;
close $fh;

[download]
The debug output is as follows: 

  DB<1> c 42
main::(grab-images.pl:42):      mark_blob(my $pic);
  DB<2> n
main::(grab-images.pl:43):      $pic = $snapshot->image;  #debug
  DB<2>
main::(grab-images.pl:45):      my $SaveFile = join("","$ImagePath{$ke
+y}",&timestamp,"\-snapshot\-$key.jpg");
  DB<2>
main::(grab-images.pl:46):      print ("Save filename: $SaveFile");
  DB<2>
main::(grab-images.pl:48):      open(my $fh, ">$SaveFile") || die "$Sa
+veFile: $!";
  DB<2> Save filename: /var/images/trackcam1/2017-04-23_20:40:01-snaps
+hot-1.jpg
main::(grab-images.pl:49):      binmode $fh;  # for MSDOS derivations.
  DB<2>
main::(grab-images.pl:50):      print $fh $pic;
  DB<2> s
Use of uninitialized value $pic in print at grab-images.pl line 50.
 at grab-images.pl line 50.
main::(grab-images.pl:51):      close $fh;

[download]

In reply to Use of uninitialized value $pic by dazz

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