X-Git-Url: https://fleuret.org/cgi-bin/gitweb/gitweb.cgi?p=finddup.git;a=blobdiff_plain;f=finddup.1;h=2da4ee3dc12e5b24d40182090bd9cfca0d4e2943;hp=691e910cd1ba52bb3787fa4f4648d6ed6b22cdbc;hb=8c988a4aca00501c9a9d53f4ff228dcb0bce0acb;hpb=f7bb05fb425e5ff6f1e9105cd36309786963825d

diff --git a/finddup.1 b/finddup.1
index 691e910..2da4ee3 100644
--- a/finddup.1
+++ b/finddup.1
@@ -10,22 +10,25 @@ finddup \- Find files common to two directories (or not)
 
 .SH "SYNOPSIS"
 
-\fBfinddup\fP [OPTION]... DIR1 [[and:|not:]DIR2]
+\fBfinddup\fP [OPTION]... [DIR1 [[and:|not:]DIR2]]
 
 .SH "DESCRIPTION"
 
-With a single directory argument, \fBfinddup\fP prints the duplicated
-files found in it. 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 you have a directory name starting with `not:'.
+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
+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
 reasonably fast.
 
-When looking for identical files, \fBfinddup\fP associates by default
-a group ID to every content, and prints it along the file names. Use
-the \fB-g\fP to switch it off.
+When looking for identical files, \fBfinddup\fP associates a group ID
+to every content, and prints it along the file names. Use the \fB-g\fP
+to switch it off.
 
 Note that
 .B finddup DIR
@@ -64,15 +67,24 @@ files with same inode are considered as different
 
 None known, probably many. Valgrind does not complain though.
 
+The current algorithm is dumb, as it does not use any hashing of the
+file content.
+
+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 never read entirely hence the md5s can not be properly computed,
+(2) computing XOR of the first 4, 16 and 256 bytes with rejection as
+soon as one does not match, (3) reading parts of the files of
+increasing sizes so that rejection could be done with a small fraction
+when possible, (4) using mmap instead of open/read.
+
 .SH "WISH LIST"
 
 The format of the output should definitely be improved. Not clear how.
 
-The comparison algorithm could definitely use some MD5 kind of
-signature. However, I doubt it would improve speed much.
-
-Their should be some fancy option to link two instances of the command
-running on different machines to reduce network disk accesses.
+Their could be some fancy option to link two instances of the command
+running on different machines to reduce network disk accesses. This
+may not help much though.
 
 .SH "EXAMPLES"
 
@@ -80,7 +92,8 @@ running on different machines to reduce network disk accesses.
 
 .fi
 List duplicated files in directory ./blah/, show a progress bar,
-ignore empty files and files and directories starting with a dot.
+ignore empty files, and ignore files and directories starting with a
+dot.
 
 .P
 .B finddup sources not:/mnt/backup
@@ -90,11 +103,12 @@ List all files found in \fB./sources/\fR which do not have
 content-matching equivalent in \fB/mnt/backup/\fR.
 
 .P
-.B finddup tralala cuicui
+.B finddup -g tralala cuicui
 
 .fi
 List groups of files with same content which exist both in
-\fB./tralala/\fR and \fB./cuicui/\fR.
+\fB./tralala/\fR and \fB./cuicui/\fR. Do not show group IDs, instead
+write an empty lines between groups of files of same content.
 
 .SH "AUTHOR"