Provided by: duff_0.5.2-1.1build1_amd64 
NAME
duff — duplicate file finder
SYNOPSIS
duff [-0HLPaeqprtz] [-d function] [-f format] [-l limit] [file ...]
duff [-h]
duff [-v]
DESCRIPTION
The duff utility reports clusters of duplicates in the specified files and/or directories. In the
default mode, duff prints a customizable header, followed by the names of all the files in the cluster.
In excess mode, duff does not print a header, but instead for each cluster prints the names of all but
the first of the files it includes.
If no files are specified as arguments, duff reads file names from stdin.
Note that as of version 0.4, duff ignores symbolic links to files, as that behavior was conceptually
broken. Therefore, the -H, -L and -P options now apply only to directories.
The following options are available:
-0 If reading file names from stdin, assume they are null-terminated, instead of separated by
newlines. Also, when printing file names and cluster headers, terminate them with null
characters instead of newlines.
This is useful for file names containing whitespace or other non-standard characters.
-H Follow symbolic links listed on the command line. This overrides any previous -L or -P option.
Note that this only applies to directories, as symbolic links to files are never followed.
-L Follow all symbolic links. This overrides any previous -H or -P option. Note that this only
applies to directories, as symbolic links to files are never followed.
-P Don't follow any symbolic links. This overrides any previous -H or -L option. This is the
default. Note that this only applies to directories, as symbolic links to files are never
followed.
-a Include hidden files and directories when searching recursively.
-d function
The message digest function to use. The supported functions are sha1, sha256, sha384 and sha512.
The default is sha1.
-e Excess mode. List all but one file from each cluster of duplicates. Also suppresses output of
the cluster header. This is useful when you want to automate removal of duplicate files and
don't care which duplicates are removed.
-f format
Set the format of the cluster header. If the header is set to the empty string, no header line
is printed.
The following escape sequences are available:
%n The number of files in the cluster.
%c A legacy synonym for %d, for compatibility reasons.
%d The message digest of files in the cluster. This may not be combined with -t as no
digest is calculated.
%i The one-based index of the file cluster.
%s The size, in bytes, of a file in the cluster.
%% A ‘%’ character.
The default format string when using -t is:
%n files in cluster %i (%s bytes)
The default format string for other modes is:
%n files in cluster %i (%s bytes, digest %d)
-h Display help information and exit.
-l limit
The minimum size of files to be sampled. If the size of files in a cluster is equal or greater
than the specified limit, duff will sample and compare a few bytes from the start of each file
before calculating a full digest. This is stricly an optimization and does not affect which
files are considered by duff. The default limit is zero bytes, i.e. to use sampling on all
files.
-q Quiet mode. Suppress warnings and error messages.
-p Physical mode. Make duff consider physical files instead of hard links. If specified, multiple
hard links to the same physical file will not be reported as duplicates.
-r Recursively search into all specified directories.
-t Thorough mode. Distrust digests as a guarantee for equality. In thorough mode, duff compares
files byte by byte when their sizes match.
-v Display version information and exit.
-z Do not consider empty files to be equal. This option prevents empty files from being reported as
duplicates.
EXAMPLES
The command:
duff -r foo/
lists all duplicate files in the directory foo and its subdirectories.
The command:
duff -e0 * | xargs -0 rm
removes all duplicate files in the current directory. Note that you have no control over which files in
each cluster that are selected by -e (excess mode). Use with care.
The command:
find . -name '*.h' -type f | duff
lists all duplicate header files in the current directory and its subdirectories.
The command:
find . -name '*.h' -type f -print0 | duff -0 | xargs -0 -n1 echo
lists all duplicate header files in the current directory and its subdirectories, correctly handling file
names containing whitespace. Note the use of xargs and echo to remove the null separators again before
listing.
DIAGNOSTICS
The duff utility exits 0 on success, and >0 if an error occurs.
SEE ALSO
find(1), xargs(1)
AUTHORS
Camilla Berglund <elmindreda@elmindreda.org>
BUGS
duff doesn't check whether the same file has been specified twice on the command line. This will lead it
to report files listed multiple times as duplicates when not using -p (physical mode). Note that this
problem only affects files, not directories.
duff no longer (as of version 0.4) reports symbolic links to files as duplicates, as they're by
definition always duplicates. This may break scripts relying on the previous behavior.
If the underlying files are modified while duff is running, all bets are off. This is not really a bug,
but it can still bite you.
Debian January 18, 2012 DUFF(1)