Why does perl remove the file extension when redirecting url via CMD? - perl

Question

I am at age 13 attempting to learn Perl. Here is one of my first scripts. The link brings the user to a webpage which downloads an image. As some observant people may notice the link has the ending of .png which specifies the image in the url. When I run this script it opens Chrome, opens the url BUT fails to include the extension .png . My questions are:
A) Why is this happening?
B) Can anyone suggest an alternative and or fix my script.
The script is found here below.
#!/usr/bin/perl
print "Type Username Here:
";
$username = <>;
print "Link: http://s3.amazonaws.com/MinecraftSkins/$username.png
";
exec "start www.s3.amazonaws.com/MinecraftSkins/$username.png";
Please help!!!

Answer 1

When you capture the data, you are also capturing the new line at the end of it.
This gives you:
exec "start www.s3.amazonaws.com/MinecraftSkins/EXAMPLE
.png";
Remove the whitespace from the end of the entered data to avoid this.
$username =~ s/\s+$//;
or
chomp($username);

Answer 2

$username will include the carriage-return you hit when you hit "enter" at the input prompt, so your exec call actually looks like two separate commands:
start www.s3.amazonaws.com/MinecraftSkins/$username
.png
Try chomp($username) to strip off that whitespace.

Answer 3

You have to whipe the newline at end of your input:
#!/usr/bin/perl
print "Type Username Here:
";
chomp ( $username = <> );
print "Link: http://s3.amazonaws.com/MinecraftSkins/$username.png
";
exec "start www.s3.amazonaws.com/MinecraftSkins/$username.png";
You could sanitize (ensure that user input contain only letters, numbers and/or the character underscore _, for sample) you variable by:
#!/usr/bin/perl
print "Type Username Here:
";
$username = $1 if <> =~ /^([a-z0-9_]*)$/i;
print "Link: http://s3.amazonaws.com/MinecraftSkins/$username.png
";
exec "start www.s3.amazonaws.com/MinecraftSkins/$username.png";
Better written (as #KeithThompson comment):
#!/usr/bin/perl
print "Type Username Here:
";
if ( <> =~ /^([a-z0-9_]*)$/i ) {
$username = $1
print "Link: http://s3.amazonaws.com/MinecraftSkins/$username.png\n";
exec "start www.s3.amazonaws.com/MinecraftSkins/$username.png";
} else {
print "Error input contain invalid characters\n";
};