Add some basic docs

README.md

@@ -1,2 +1,112 @@
 # finddupes
-finds duplicate files based on hash and deletes them based on a given pattern
+
+Finds duplicate files based on hash and deletes them based on a given pattern.
+
+
+## Background
+
+`finddupes` tries to be efficient by
+
+- comparing file size before running expensive hash caluculations
+- using hash tables to find duplicate sizes/hashes in constant time on avg
+- using the fast [xxHash](https://github.com/Cyan4973/xxHash) algorithm to calulcate hashes
+- running things in parallel. However, this only really helps if directories to be searched for reside on different media
+- using an optional "cache" that can be reused and extended for multiple searches/deletions
+
+What does `finddupes` not do
+
+- try to find very similar files (fuzzy search)
+
+## Usage
+
+Run finddupes with the `-help` flag to get all options:
+
+    finddupes -help
+
+The exection can be interruped with `Ctrl-c`. This will gracefully finish all calulcation
+and write operations before shutting down.
+
+### Find duplicates in given directories
+
+This will list all found duplicates.
+
+    finddupes <path> [path...]
+
+Depending on the amount and size of files this can take a long time. For a large amount of files
+it is recommended to index all duplicates and store them in a database file.
+See next section.
+
+### Index files
+
+Index all files from given directories recursively and store them in a database file.
+
+    finddupes -verbose -storeonly -path <db file path> <path> [path...]
+
+e.g.
+
+    finddupes -verbose -storeonly -path pics.db ~/Pictures ~/Videos ~/DCIM
+
+
+After indexing files one or more actions can be run to delete duplicates.
+A single last file will be always kept, regardless if there's a match or not.
+
+The default is a dry run. To actually delete files, add the `-delete` flag.
+
+
+Alternatively to indexing first, all actions can be run on the fly by not passing
+the `-path <db file path>` parameter.
+
+    finddupes -delmatch <pattern> ~/Pictures ~/Videos
+
+See the next sections for a list of possible actions.
+
+
+### Delete duplicates based on a pattern
+
+Delete duplicates whose path matches the given regex.
+
+    finddupes -path <db file path> -delmatch <pattern>
+
+e.g.
+
+    finddupes -path pics.db -delmatch '\.jpe?g$'
+
+
+#### Keep duplicates based on a pattern
+
+Keep duplicates whose path matches the given regex.
+
+    finddupes -path <db file path> -keepmatch <pattern>
+
+e.g.
+
+    finddupes -path pics.db -keepmatch '_orignal$'
+
+
+### Keep most recent duplicate
+
+Keep the most recent duplicate, delete all others. Based on modification time (mtime).
+
+    finddupes -path <db file path> -keeprecent
+
+
+### Keep oldest duplicate
+
+Keep the oldest duplicate, delete all others. Based on modification time (mtime).
+
+    finddupes -path <db file path> -keepoldest
+
+
+### Keep first duplicate
+
+Keep the first duplicate based on lexically sorted file *paths* (not file names), delete all others.
+
+    finddupes -path <db file path> -keepfirst
+
+
+### Keep last duplicate
+
+Keep the last duplicate based on lexically sorted file *paths* (not file names), delete all others.
+
+    finddupes -path <db file path> -keeplast
+