I had the problem that the Md5 Sum of a file changed after copying it to my external disk.

This unhandy command helped me to fix the problem.

Use zsh process substitution syntax.

This is a beginning script. You can create a file with > filename. You can also use diff to compare output run at different times to verify no change in your files. I apologize in advance if this is too simple. For some it should be a start.

Improvement of the command "Find Duplicate Files (based on size first, then MD5 hash)" when searching for duplicate files in a directory containing a subversion working copy. This way the (multiple dupicates) in the meta-information directories are ignored.

Can easily be adopted for other VCS as well. For CVS i.e. change ".svn" into ".csv":

A bit shorter and parallelized. Depending on the speed of your cpu and your disk this may run faster.

Parallel is from https://savannah.nongnu.org/projects/parallel/

All valid files are withheld so only failures show up. No output, all checks good.

usage: sitepass MaStErPaSsWoRd example.com

description: An admittedly excessive amount of hashing, but this will give you a pretty secure password, It also eliminates repeated characters and deletes itself from your command history.

tr '!-~' 'P-~!-O' # this bit is rot47, kinda like rot13 but more nerdy

rev # this avoids the first few bytes of gzip payload, and the magic bytes.

This dup finder saves time by comparing size first, then md5sum, it doesn't delete anything, just lists them.

This can be much faster than downloading one or both trees to a common servers and comparing the files there. After, only those files could be copied down for deeper comparison if needed.

Calculates md5 sum of files. sort (required for uniq to work). uniq based on only the hash. use cut ro remove the hash from the result.

A useful way to generate the MD5 hash for a string by command line

This was useful to generate random passwords to some webpage users, using the sample code, inside a bash script

[re]verify those burned CD's early and often - better safe than sorry -

at a bare minimum you need the good old `dd` and `md5sum` commands,

but why not throw in a super "user-friendly" progress gauge with the `pv` command -

adjust the ``-s'' "size" argument to your needs - 700 MB in this case,

and capture that checksum in a "test.md5" file with `tee` - just in-case for near-future reference.

*uber-bonus* ability - positively identify those unlabeled mystery discs -

for extra credit, what disc was used for this sample output?

For quick validation of folder's file-contents (structure not taken into account) - I use it mostly to check if two folders' contents are the same.

Original author unknown (I believe off of a wifi hacking forum).

Used in conjuction with ifconfig and cron.. can be handy (especially spoofing AP's)

Found this little gem here: http://info.michael-simons.eu/2008/10/25/recursively-md5sum-all-files-in-a-directory-tree/