So I have a space/new line after a closing ?> (php tag) that is breaking my application.
How can I find it easily I have 1000 of files and 100000 lin
The problem here is normal grep doesn't match multiple lines. So, I would install pcregrep and try the following command:
pcregrep -rMl '\?>[\s\n]+\z' *
This will match all files in the folder and subfolders (the -r part) using PCRE multiline match (the -M part), and only list their filenames (the -l part).
As for the pattern, well that matches ?> followed by 1 or more whitespace or newline characters, followed by the end of the file \z. I found though, when I ran this on my folder, many of the PHP files do in fact end with a single newline. So you can update that regex to be '\?>[\s\n]+\n\z' to match files with whitespace over and above the single \n character terminator.
Lastly, you can always use od -c filename to print unambiguous representation of the file if you need to check its exact character sequence ending.