Fixes and other updates to 1998/schweikh3

The constant that was in the code was changed to a macro in the Makefile
called SZ. Though it's highly unlikely that this will ever be needed the
author noted that increasing the value has some merit in a rare case so
it's now easier to do this (though one might have to type more,
admittedly, as all the -D options have to be specified but it no longer
is required to modify the code).

The README.md file has been format and typo checked. I did change the
way the man page was displayed (in the README.md) so this has to be
verified to look good but everything else should be good anyway.

The try.sh script I added was updated to have another command that was
in the judges' remarks. Instead it's now all in the try section and the
judges' remarks just have the comments, not the command to try.

When I updated the thanks file I noticed a couple things that could be
clarified in another entry so those minor fixes were made too but have
no relation to this commit.
This commit is contained in:
Cody Boone Ferguson committed 2023-11-12 05:37:03 -08:00
1 parent 3141392cc1
commit ca256ce440
5 files changed
+85 -54

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+1 -1
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@@ -58,7 +58,7 @@ ARCH=
# Defines that are needed to compile
#
CDEFINE= -DM0=sizeof -DM1=long -DM2=void \
-DM3=realloc -DM4=calloc -DM5=free
-DM3=realloc -DM4=calloc -DM5=free -DSZ=32767
# Include files that are needed to compile
#
+60 -46
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@@ -4,10 +4,29 @@
make all
```
The author stated:
```
In the remote event that the input has more than `8192` files with
the same size (on systems where `sizeof (char *) == 4`, or `4096` when
`sizeof (char *) == 8`), increase the manifest constant 32767 on line
31.
```
so we changed the constant to be `SZ` defined in the Makefile. To change the
value you can do something like:
```sh
make clobber CDEFINE="-DM0=sizeof -DM1=long -DM2=void \
-DM3=realloc -DM4=calloc -DM5=free -DSZ=55555" all
```
or whatever you wish to redefine it to.
## To use:
If "dir" is the directory (or a directory tree) where you keep
If `dir` is the directory (or a directory tree) where you keep
all your favorite pictures off the Internet or from
`alt.binaries.pictures.*`, do
@@ -15,7 +34,7 @@ all your favorite pictures off the Internet or from
find dir -type f -print | ./samefile
```
Maybe you will not need to buy another 10 Gb disk to store them. :-)
Maybe you will not need to buy another 10 GB disk to store them. :-)
### Try:
@@ -23,20 +42,14 @@ Maybe you will not need to buy another 10 Gb disk to store them. :-)
If you're in this winning entry's directory:
```sh
find . -type f -print | ./samefile
./try.sh
```
Notice that the tool finds a duplicate file, that of the man page.
Notice that the tool finds some files that are duplicates.
## Judges' remarks:
Try this:
```sh
./try.sh
```
This program is not as smart as to detect identity of JPEG files with the same
picture but with different compression levels. On the other hand compression can
make a thing look/sound/feel different so these probably aren't duplicates
@@ -56,7 +69,7 @@ Thank God the IEEE does not standardize a coding style...
### What this program does
This is best explained in the man page. The troff source for this
man page can be found in the file samefile.1. To render try:
man page can be found in the file [samefile.1](samefile.1). To render try:
```sh
`man ./samefile.1
@@ -65,23 +78,24 @@ man page can be found in the file samefile.1. To render try:
Otherwise:
**SAMEFILE(1) User Manuals SAMEFILE(1)**
### SAMEFILE(1) User Manuals SAMEFILE(1)
**NAME**
#### NAME
**samefile** - find identical files
`samefile` - find identical files
**SYNOPSIS**
#### SYNOPSIS
./samefile
```sh
./samefile
```
**DESCRIPTION**
#### DESCRIPTION
`samefile` reads a list of file names (one file name per
line) from `stdin`. For each file name pair with identical
line) from `stdin`. For each file name pair with identical
contents, a line consisting of six tab separated fields is
output: The size in bytes, two file names, the character
`=` if the two files are on the same device, `X` otherwise,
@@ -104,10 +118,10 @@ binary tree.
In the second stage all files having the same size are
compared against each other. The rules of mathematical
logic are applied to reduce work and output noise: if
files A, B, and C have the same size and samefile finds
that A = B and A = C then it will not compare B against C
(and will not output a line for B and C) but only for A =
B and A = C. The algorithm will detect equality across
files `A`, `B`, and `C` have the same size and samefile finds
that `A = B` and `A = C` then it will not compare `B` against `C`
(and will not output a line for `B` and `C`) but only for `A =
B` and `A = C`. The algorithm will detect equality across
arbitrarily long chains. Note however, that because only
the first filename per inode gets into the first stage,
the output for a group of identical files with different
@@ -116,13 +130,13 @@ identical files of size 100 in an inode group consisting
of the three inodes with numbers 10, 20 and 30:
```sh
$ ls -i # output edited for readability:
10 file1 20 file4 30 file6
10 file2 20 file5
10 file3
$ ls | ./samefile
100 file1 file4 = 3 2
100 file1 file6 = 3 1
$ ls -i # output edited for readability:
10 file1 20 file4 30 file6
10 file2 20 file5
10 file3
$ ls | ./samefile
100 file1 file4 = 3 2
100 file1 file6 = 3 1
```
The sum of the sizes in the first column is the amount of
@@ -135,24 +149,24 @@ Note that it is not enough to just remove `file4` and `file6`
exists.)
**LIMITATIONS**
#### LIMITATIONS
`samefile` was written with no limits in mind. The number of
input lines is unlimited. The size of the actual files is
only limited by available virtual memory needed to compare
one pair of files. The only hard limit is the constraint
that there should not be more than about 8192 files having
that there should not be more than about `8192` files having
the same size. Experience has shown that there are rarely
more than a couple dozen files of the same size.
**EXAMPLES**
#### EXAMPLES
For everybody:
What are the duplicates under my home directory?
```sh
$ find $HOME | ./samefile
find $HOME | ./samefile
```
For the sysadmin folks:
@@ -160,23 +174,23 @@ For the sysadmin folks:
Report all duplicate files under /usr larger than 16k:
```sh
$ find /usr -size +16384c -a -type f | ./samefile
find /usr -size +16384c -a -type f | ./samefile
```
For the ftp and WWW admins:
How much space is wasted below our site's /pub directory?
```sh
$ find /pub -type f | samefile | awk '{sum += $1} END {print sum}'
find /pub -type f | samefile | awk '{sum += $1} END {print sum}'
```
**EXIT STATUS**
#### EXIT STATUS
If `samefile` runs out of memory the exit status is 1, zero
otherwise.
**SEE ALSO**
#### SEE ALSO
`find(1)`, `ln(1)`, `rm(1)`
@@ -194,19 +208,19 @@ otherwise.
of files across arbitrarily long chains? In my private unobfuscated
source there are 17 lines describing just that. A classical case for
the well known `/* You're not supposed to understand this */` comment.
- Would Dijkstra consider this goto harmful?
- The only string literal is split in more than a dozen substrings
- Would Dijkstra consider this `goto` harmful?
- The only string literal is split in more than a dozen substrings.
- For the task at hand the code is pretty terse. Some dynamic memory
is even freed as soon as it's no longer needed. I have tried to
make the preprocessor directives as short as possible. This means
no spaces after #include and no spaces after some of the macro
no spaces after `#include` and no spaces after some of the macro
names.
Are you an algorithms guru? If so you should know why the output
appears sorted without any use of `qsort()` or `system("sort")`.
appears sorted without any use of `qsort(3)` or `system("sort")`.
Rewrite (hah!) the program to use memory mapping of files instead
of `read()`. Does this affect performance noticeably?
of `read(2)`. Does this affect performance noticeably?
It's easy to write a script that takes `samefile`'s output and
hard links (or symlinks) identical files. Writing such a script is
@@ -214,11 +228,11 @@ left as an exercise for the deobfuscator.
When you run `samefile` on some directory tree, try to estimate
how much you think it will find. Is the actual result anywhere
near your estimate? How many copies of the GPL COPYING file
near your estimate? How many copies of the GPL `COPYING` file
are there on your filesystems? :-)
In the remote event that the input has more than 8192 files with
the same size (on systems where `sizeof (char *) == 4`, or 4096 when
In the remote event that the input has more than `8192` files with
the same size (on systems where `sizeof (char *) == 4`, or `4096` when
`sizeof (char *) == 8`), increase the manifest constant 32767 on line
31.
+1 -1
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@@ -28,7 +28,7 @@
/* HE WHO SAYS */
Z I A<:32767/ M0(I )]; Z g stat S,T; Z size_t y B f{
Z I A<: SZ/ M0(I )]; Z g stat S,T; Z size_t y B f{
I n ; g f * x ; dev_t d ; ino_t i; } f B t{ M1 s,c; f
*l; g t*L,*R; } t; D(a,t)D(E ,f)Z t*J(t*p,I n){ H! p){ p=
a(); p _ s =S O; p _ c=1; p _ L=p _ R=0;
+3
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@@ -12,3 +12,6 @@ echo "$ ln -f file3 file4"
ln -f file3 file4
echo "$ find . -type f -name 'file?' | ./samefile"
find . -type f -name 'file?' | ./samefile
echo "find . -type f -print | ./samefile" 1>&2
find . -type f -print | ./samefile
+20 -6
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@@ -2163,6 +2163,19 @@ command.
Cody also made the Makefile rule `all` symlink the entry to `samefile` as that
is the name of the program.
The author stated that:
```
In the remote event that the input has more than `8192` files with
the same size (on systems where `sizeof (char *) == 4`, or `4096` when
`sizeof (char *) == 8`), increase the manifest constant 32767 on line
31.
```
so Cody changed the constant to a macro in the Makefile called `SZ` so one can
more easily do this (though it indeed seems highly unlikely). See the README.md
for more details.
There actually is a web page for the tool and this was added to the author
information for the entry. It has not been added to any JSON file.
@@ -2170,12 +2183,13 @@ information for the entry. It has not been added to any JSON file.
## [1998/tomtorfs](1998/tomtorfs/tomtorfs.c) ([README.md](1998/tomtorfs/README.md]))
Cody fixed the assumption that `EOF` is `-1` (the author noted that it assumes
it is `-1` but the standard only guarantees that it's a value `< 0`) and that 1
is a valid code to return failure (it seems unlikely that it wouldn't be but
since the author suggested it it was changed to `EXIT_FAILURE`). To make it so
the lines end at the same columns as the original the `EXIT_FAILURE` change was
done by redefining `exit(3)` to be `exit(a) return EXIT_FAILURE` and `1` was
passed to it (`return` was used because the original program had `return 1`).
it is `-1` and it's indeed a valid concern as the standard only guarantees that
it's a value `< 0`) and that `1` is a valid code to return failure (it seems
unlikely that it wouldn't be but since the author suggested it it was changed to
`EXIT_FAILURE`). To make it so the lines end at the same columns as the original
the `EXIT_FAILURE` change was done by redefining `exit(3)` to be `exit(a) return
EXIT_FAILURE` and `1` was passed to it (`return` was used because the original
program had `return 1`).
Cody also added the [try.sh](1998/tomtorfs/try.sh) script to try out a few
commands that we recommended.