duff — duplicate file finder

       Camilla Berglund <elmindreda@elmindreda.org>

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)

       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.

       -dfunction
               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.

       -fformat
               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:

                     %nfilesincluster%i(%sbytes)

               The default format string for other modes is:

                     %nfilesincluster%i(%sbytes,digest%d)-h      Display help information and exit.

       -llimit
               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.

       The duff utility exits 0 on success, and >0 if an error occurs.

       The command:
             duff-rfoo/

       lists all duplicate files in the directory foo and its subdirectories.

       The command:
             duff-e0*|xargs-0rm

       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'-typef|duff

       lists all duplicate header files in the current directory and its subdirectories.

       The command:
             find.-name'*.h'-typef-print0|duff-0|xargs-0-n1echo

       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.

       duff — duplicate file finder

find(1), xargs(1)

duff [-0HLPaeqprtz] [-dfunction] [-fformat] [-llimit] [file...]
       duff [-h]
       duff [-v]