September 2011 Archives

poor man's cfv/cksfv (CRC checksum)

Lately I wanted to compute CRC-32 checksums for some videos. At first, I took a look at Digest::CRC and wrote this one-liner:

perl -MDigest::CRC=crc32_hex -E 'say crc32_hex <>' file.mkv

But of course that didn't work, since I was only reading a line off the first file in @ARGV. Realizing I need to read in the file, I added IO::All in the mix:

perl -MDigest::CRC=crc32_hex -MIO::All -E 'say crc32_hex io($ARGV[0])->all' file.mkv

That worked, but it was too slow since it read files into a string, and I was dealing with large (~1GB) file sizes. After a bit of looking around, I found the Digest::file module, so my one-liner finally becomes:

perl -MDigest::file=digest_file_hex -E 'say "$_ cksum: \U@{[digest_file_hex $_, q|CRC-32|]}\E" for @ARGV' file1.mkv file2.mkv files*.avi

Of course, I could have gotten something like cfv or cksfv from my Ubuntu repository, but curiosity got the better of me ;)

(edited: make use of perl's -E switch to implicitly enable features.)

About Zak B. Elep

user-pic Hacker, Gamer, Married. Runs Slackware on laptops, OpenBSD on servers, and Perl on everything. Even on Docker.