X-Git-Url: https://fleuret.org/cgi-bin/gitweb/gitweb.cgi?a=blobdiff_plain;f=finddup.1;h=46a4326fb9f2e1244aef1bfe9a93588f43505880;hb=0d200c3b81ec3672daea4cffd15551e4e3788d9d;hp=691e910cd1ba52bb3787fa4f4648d6ed6b22cdbc;hpb=f7bb05fb425e5ff6f1e9105cd36309786963825d;p=finddup.git

diff --git a/finddup.1 b/finddup.1
index 691e910..46a4326 100644
--- a/finddup.1
+++ b/finddup.1
@@ -15,17 +15,19 @@ finddup \- Find files common to two directories (or not)
 .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:'.
+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:'.
 
 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
@@ -59,20 +61,35 @@ 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-m\fR, \fB--md5\fR
+use MD5 hashing
 
 .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).
+
+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.
+
+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.
+
 .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. Again,
+this may not help much, for the reason given above.
 
 .SH "EXAMPLES"
 
@@ -80,7 +97,8 @@ 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 +108,12 @@ 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"