1DUFF(1) BSD General Commands Manual DUFF(1)
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4 duff — duplicate file finder
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7 duff [-0HLPaeqprtz] [-d function] [-f format] [-l limit] [file ...]
8 duff [-h]
9 duff [-v]
10
12 The duff utility reports clusters of duplicates in the specified files
13 and/or directories. In the default mode, duff prints a customizable
14 header, followed by the names of all the files in the cluster. In excess
15 mode, duff does not print a header, but instead for each cluster prints
16 the names of all but the first of the files it includes.
17 If no files are specified as arguments, duff reads file names from stdin.
19 Note that as of version 0.4, duff ignores symbolic links to files, as
21 that behavior was conceptually broken. Therefore, the -H, -L and -P
22 options now apply only to directories.
23 The following options are available:
25 -0 If reading file names from stdin, assume they are null-termi‐
27 nated, instead of separated by newlines. Also, when printing
28 file names and cluster headers, terminate them with null charac‐
29 ters instead of newlines.
30 This is useful for file names containing whitespace or other non-
32 standard characters.
33 -H Follow symbolic links listed on the command line. This overrides
35 any previous -L or -P option. Note that this only applies to
36 directories, as symbolic links to files are never followed.
37 -L Follow all symbolic links. This overrides any previous -H or -P
39 option. Note that this only applies to directories, as symbolic
40 links to files are never followed.
41 -P Don't follow any symbolic links. This overrides any previous -H
43 or -L option. This is the default. Note that this only applies
44 to directories, as symbolic links to files are never followed.
45 -a Include hidden files and directories when searching recursively.
47 -d function
49 The message digest function to use. The supported functions are
50 sha1, sha256, sha384 and sha512. The default is sha1.
51 -e Excess mode. List all but one file from each cluster of dupli‐
53 cates. Also suppresses output of the cluster header. This is
54 useful when you want to automate removal of duplicate files and
55 don't care which duplicates are removed.
56 -f format
58 Set the format of the cluster header. If the header is set to
59 the empty string, no header line is printed.
60 The following escape sequences are available:
62 %n The number of files in the cluster.
64 %c A legacy synonym for %d, for compatibility reasons.
66 %d The message digest of files in the cluster. This may
68 not be combined with -t as no digest is calculated.
69 %i The one-based index of the file cluster.
71 %s The size, in bytes, of a file in the cluster.
73 %% A ‘%’ character.
75 The default format string when using -t is:
77 %n files in cluster %i (%s bytes)
79 The default format string for other modes is:
81 %n files in cluster %i (%s bytes, digest %d)
83 -h Display help information and exit.
85 -l limit
87 The minimum size of files to be sampled. If the size of files in
88 a cluster is equal or greater than the specified limit, duff will
89 sample and compare a few bytes from the start of each file before
90 calculating a full digest. This is stricly an optimization and
91 does not affect which files are considered by duff. The default
92 limit is zero bytes, i.e. to use sampling on all files.
93 -q Quiet mode. Suppress warnings and error messages.
95 -p Physical mode. Make duff consider physical files instead of hard
97 links. If specified, multiple hard links to the same physical
98 file will not be reported as duplicates.
99 -r Recursively search into all specified directories.
101 -t Thorough mode. Distrust digests as a guarantee for equality. In
103 thorough mode, duff compares files byte by byte when their sizes
104 match.
105 -v Display version information and exit.
107 -z Do not consider empty files to be equal. This option prevents
109 empty files from being reported as duplicates.
110
112 The command:
113 duff -r foo/
114 lists all duplicate files in the directory foo and its subdirectories.
116 The command:
118 duff -e0 * | xargs -0 rm
119 removes all duplicate files in the current directory. Note that you have
121 no control over which files in each cluster that are selected by -e
122 (excess mode). Use with care.
123 The command:
125 find . -name '*.h' -type f | duff
126 lists all duplicate header files in the current directory and its subdi‐
128 rectories.
129 The command:
131 find . -name '*.h' -type f -print0 | duff -0 | xargs -0 -n1 echo
132 lists all duplicate header files in the current directory and its subdi‐
134 rectories, correctly handling file names containing whitespace. Note the
135 use of xargs and echo to remove the null separators again before listing.
136
138 The duff utility exits 0 on success, and >0 if an error occurs.
139
141 find(1), xargs(1)
142
144 Camilla Berglund <elmindreda@elmindreda.org>
145
147 duff doesn't check whether the same file has been specified twice on the
148 command line. This will lead it to report files listed multiple times as
149 duplicates when not using -p (physical mode). Note that this problem
150 only affects files, not directories.
151 duff no longer (as of version 0.4) reports symbolic links to files as
153 duplicates, as they're by definition always duplicates. This may break
154 scripts relying on the previous behavior.
155 If the underlying files are modified while duff is running, all bets are
157 off. This is not really a bug, but it can still bite you.
158BSD January 18, 2012 BSD