X-Git-Url: https://www.fleuret.org/cgi-bin/gitweb/gitweb.cgi?a=blobdiff_plain;f=finddup.1;h=94e31b28df3c181d836cd0c23db0be1f90c650e2;hb=99891f9faf2d2e6313551df902856469e4514595;hp=18c27e5f57def998cccccfbcbfb1c3bc3907fe48;hpb=c54c57cbd82dd37632d9ed551ebab0c1489dfd69;p=finddup.git

diff --git a/finddup.1 b/finddup.1
index 18c27e5..94e31b2 100644
--- a/finddup.1
+++ b/finddup.1
@@ -10,12 +10,13 @@ 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 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
@@ -66,17 +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 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.
 
-The comparison algorithm could maybe be improved with some MD5 kind of
-signature. However, most of the time is taken by comparison for
-matching files, which are required even when using a hash.
-
 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"