ImageMagick not working, and not giving error messages either

I have some Perl code I wrote for a client which, in part, resizes images using ImageMagick's convert.

This was done via backticks, capturing the output in this way:

$output = `convert foo.jpg foo.gif 2>&1`; # simplified example

Recently my client's hosting company made what he was told were "DNS changes", and since that date*, the command doesn't work, and not only that, there's no $output either.

Assuming something has happened like him being moved to a server which hasn't got ImageMagick, or a botched install or update of the library -- shouldn't I be getting something back from that? At least a "convert not found"? I've tried with system() as well and it's the same. Image not converted, nothing comes back.

Unfortunately, command-line access is not available.

* 开发者_StackOverflowI suppose this could actually be a coincidence.

You can use convert's debug option to find out what it's doing.

To capture all outputs of a shell command use Capture::Tiny like this:

use Capture::Tiny 'capture';

my @command = qw( convert foo.jpg foo.gif );

my $return_code;
my ($stdout, $stderr) = capture {
    $return_code = system( @command );
};

$stdout and $stderr will contain what it says on the tin. $return_code will return the return code of the task itself, which is traditionally 0 when successful or a non-zero numerical value when an error happened.

They may have no shell installed (think of perl/mod_perl being run in a chroot), such that backticks cannot be executed at all (since they involve calling sh -c 'convert ...'. Always check $? and $!.