Cosmetics.

[finddup.git] / finddup.1

diff --git a/finddup.1 b/finddup.1
index 46a4326..b58fb43 100644 (file)
--- a/finddup.1
+++ b/finddup.1
@@ -1,4 +1,4 @@
-.TH "FINDDUP" 1 "Mar 2010" "Francois Fleuret" "User Commands"
+.TH "FINDDUP" "1.1" "Apr 2010" "Francois Fleuret" "User Commands"

 
 \" This man page was written by Francois Fleuret <francois@fleuret.org>
 \" and is distributed under a Creative Commons Attribution-Share Alike
 
 \" This man page was written by Francois Fleuret <francois@fleuret.org>
 \" and is distributed under a Creative Commons Attribution-Share Alike


@@ -10,16 +10,17 @@ finddup \- Find files common to two directories (or not)
 
 .SH "SYNOPSIS"
 
 
 .SH "SYNOPSIS"
 

-\fBfinddup\fP [OPTION]... DIR1 [[and:|not:]DIR2]
+\fBfinddup\fP [OPTION]... [DIR1 [[and:|not:]DIR2]]

 
 .SH "DESCRIPTION"
 
 
 .SH "DESCRIPTION"
 

-With a single directory argument, \fBfinddup\fP prints the duplicated
-files found in it.
+With one directory as argument, \fBfinddup\fP prints the duplicated
+files found in it. If no directory is provided, it uses the current
+one as default.

 
 With two directories, it prints either the files common to both DIR1
 and DIR2 or, with the `not:' prefix, the ones present in DIR1 and not
 
 With two directories, it prints either the files common to both DIR1
 and DIR2 or, with the `not:' prefix, the ones present in DIR1 and not

-in DIR2. The and: prefix is assumed by default and necessary only if
+in DIR2. The `and:' prefix is assumed by default and necessary only if

 you have a directory name starting with `not:'.
 
 This command compares files by first comparing their sizes, hence goes
 you have a directory name starting with `not:'.
 
 This command compares files by first comparing their sizes, hence goes


@@ -46,13 +47,16 @@ ignore files and directories starting with a dot
 ignore empty files
 .TP
 \fB-c\fR, \fB--hide-matchings\fR
 ignore empty files
 .TP
 \fB-c\fR, \fB--hide-matchings\fR

-do not show which files from DIR2 corresponds to files from DIR1
+do not show which files from DIR2 correspond to files from DIR1

 (hence, show only the files from DIR1 which have an identical twin in
 DIR2)
 .TP
 \fB-g\fR, \fB--no-group-ids\fR
 do not show the file group IDs
 .TP
 (hence, show only the files from DIR1 which have an identical twin in
 DIR2)
 .TP
 \fB-g\fR, \fB--no-group-ids\fR
 do not show the file group IDs
 .TP

+\fB-t\fR, \fB--time-sort\fR
+sort files in each group according to the modification times
+.TP

 \fB-p\fR, \fB--show-progress\fR
 show progress information in stderr
 .TP
 \fB-p\fR, \fB--show-progress\fR
 show progress information in stderr
 .TP


@@ -61,35 +65,33 @@ show the real path of the files
 .TP
 \fB-i\fR, \fB--same-inodes-are-different\fR
 files with same inode are considered as different
 .TP
 \fB-i\fR, \fB--same-inodes-are-different\fR
 files with same inode are considered as different

-.TP
-\fB-m\fR, \fB--md5\fR
-use MD5 hashing

 
 .SH "BUGS"
 
 None known, probably many. Valgrind does not complain though.
 
 
 .SH "BUGS"
 
 None known, probably many. Valgrind does not complain though.
 

-The MD5 hashing is not satisfactory. It is computed for a file only if
-the said file has to be read fully for a comparison (i.e. two files
-match and we have to read them completely).
+Since files with same inodes are considered as different when looking
+for duplicates in a single directory, there are weird behaviors -- not
+bugs -- with hard links.

 
 

-Hence, in practice lot of partial MD5s are computed, which costs a lot
-of cpu and is useless. This often hurts more than it helps, hence it
-is off by default. The only case when it should really be useful is
-when you have plenty of different files of same size, and lot of
-similar ones, which does not happen often.
+The current algorithm is dumb, as it does not use any hashing of the
+file content.

 
 

-Forcing the files to be read fully so that the MD5s are properly
-computed is not okay neither, since it would fully read certain files,
-even if we will never need their MD5s.
+Here are the things I tried, which did not help at all: (1) Computing
+md5s on the whole files, which is not satisfactory because files are
+often not read entirely, hence the md5s can not be properly computed,
+(2) computing XORs of the first 4, 16 and 256 bytes with rejection as
+soon as one does not match, (3) reading files in parts of increasing
+sizes so that rejection could be done with only a small fraction read
+when possible, (4) using mmap instead of open/read.

 
 .SH "WISH LIST"
 
 The format of the output should definitely be improved. Not clear how.
 
 Their could be some fancy option to link two instances of the command
 
 .SH "WISH LIST"
 
 The format of the output should definitely be improved. Not clear how.
 
 Their could be some fancy option to link two instances of the command

-running on different machines to reduce network disk accesses. Again,
-this may not help much, for the reason given above.
+running on different machines to reduce network disk accesses. This
+may not help much though.

 
 .SH "EXAMPLES"
 
 
 .SH "EXAMPLES"
 


@@ -113,7 +115,7 @@ content-matching equivalent in \fB/mnt/backup/\fR.
 .fi
 List groups of files with same content which exist both in
 \fB./tralala/\fR and \fB./cuicui/\fR. Do not show group IDs, instead
 .fi
 List groups of files with same content which exist both in
 \fB./tralala/\fR and \fB./cuicui/\fR. Do not show group IDs, instead

-write an empty lines between groups of files of same content.
+write empty lines between groups of files of same content.

 
 .SH "AUTHOR"
 
 
 .SH "AUTHOR"