PCRE to filter files on extension

Question

Hi,

I need a PCRE(Perl Compatible Regular Expression) that will match all non-images(jpg,png,tiff) from a list of files. So I need something go in place of XXX

# Perl
while(<>){
chomp;
if(/XXX/){
// non-image
}
}

// PHP
foreach($files as $file){    
if(preg_match('/XXX/',$file){
// non-image
}
}

I know it can be done using negation like below, but I was looking for something without using negation.

if(!/\.jpg$/)
{
}

Also please provide a brief explanation of how your Regex work, if possible

thanks in advance

Answer 1

Here's a solution using a negative lookbehind (?<! ... ):

/(?<!\.png|\.jpg|\.tiff)$/

It matches the end of the string, but only if it isn't preceded by .png, .jpg or .tiff.

Here's a Perl friendly version using only fixed width look behinds:

/(?<!\.png)(?<!\.jpg)(?<!\.tiff)$/