mogrify not working

rbhyland has asked for the wisdom of the Perl Monks concerning the following question:

I am running the code below. I want to flip the file passed in Slide_name. The mogrify command between the backticks looks correct to me, but it doesn't seem to do anything. What am I doing wrong? Appreciate any suggestions...

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

use Image::Magick;
use CGI::Carp qw(fatalsToBrowser); 
use CGI::Pretty;
use CGI qw(:standard :cgi-lib -debug fatalsToBrowser warningsToBrowser
+);

my $cgi = new CGI;

print $cgi->header;
print start_html;
my $slide_name = "../".param('slide_name');
print "$slide_name",br;
print img({-src=>"$slide_name"}),br;
`/usr/bin/mogrify -flip $slide_name`;
print img({-src=>"$slide_name"}),br;
#print redirect(referer());

print end_html;
[download]

Comment on mogrify not working Download Code

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Re: mogrify not working by onelander (Sexton) on Mar 02, 2014 at 19:48 UTC
A few points. Are you sure that slide_name is being passed? You may want to save the mogrify command output to a variable and look at what is returns. my $ret = `/usr/bin/mogrify -flip $slide_name`; print "\n" . $ret . "\n"; [download]	[reply] [d/l]
Re^2: mogrify not working by rbhyland (Acolyte) on Mar 02, 2014 at 19:53 UTC
I have printed the slide_name and it is OK. I printed the mogrify command without any parameters and got its explanatory usage text. When I print the before and after images there is no change.	[reply]
Re^2: mogrify not working by rbhyland (Acolyte) on Mar 02, 2014 at 19:57 UTC
I tried your code and it worked! But only once. When I ran the script again it didn't flip the picture back. ?!	[reply]
Re^3: mogrify not working (image caching) by kcott (Archbishop) on Mar 02, 2014 at 23:14 UTC
"I tried your code and it worked! But only once. When I ran the script again it didn't flip the picture back. ?!" It's possible the image is being cached: what's displayed in the browser may just be a copy of what was displayed from the last run. Check the actual file on disk to see if it's being flipped between runs. If it is a caching issue, you may need to set a short expiration date. See CGI: CREATING A STANDARD HTTP HEADER for details. -- Ken	[reply]
Re^2: mogrify not working by rbhyland (Acolyte) on Mar 02, 2014 at 20:01 UTC
Printing $ret gives nothing at all.	[reply]
Re^3: mogrify not working (backticks return value) by kcott (Archbishop) on Mar 02, 2014 at 23:22 UTC
"Printing $ret gives nothing at all." See perlop: Quote-Like Operators for information about what's returned by `...` and how to change it. -- Ken	[reply] [d/l]
Re^3: mogrify not working by onelander (Sexton) on Mar 02, 2014 at 20:05 UTC
I just ran that mogrify command and it does not return anything if it appears to run correctly.	[reply]