Get the number of pages in a PDF document

Question

This question is for referencing and comparing. The solution is the accepted answer below.

Many hours have I searched for a fast and easy, but mostly a

Answer 1

If you have access to shell, a simplest (but not usable on 100% of PDFs) approach would be to use grep.

This should return just the number of pages:

grep -m 1 -aoP '(?<=\/N )\d+(?=\/)' file.pdf

Example: https://regex101.com/r/BrUTKn/1

Switches description:

• -m 1 is neccessary as some files can have more than one match of regex pattern (volonteer needed to replace this with match-only-first regex solution extension)
• -a is neccessary to treat the binary file as text
• -o to show only the match
• -P to use Perl regular expression

Regex explanation:

• starting "delimiter": (?<=\/N ) lookbehind of /N (nb. space character not seen here)
• actual result: \d+ any number of digits
• ending "delimiter": (?=\/) lookahead of /

Nota bene: if in some case match is not found, it's safe to assume only 1 page exists.