Add 2018/burton1/try.sh, rename scripthd, ...
The scripthd is now called scripthd.sh to help GitHub/browsers with whether or not to download or show it. The try.sh script uses the script to show the differences between it and prog. The README.md file has been format/typo checked.
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@@ -4,6 +4,9 @@
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make
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```
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There is an alternate version of this entry. See [Alternate
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code](#alternate-code) below.
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## To use:
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@@ -15,8 +18,7 @@ make
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### Try:
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```sh
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./prog < prog
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./prog < prog.c
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./try.sh
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```
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@@ -24,15 +26,23 @@ make
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An alternate version of this entry, [prog.alt.c](prog.alt.c), is provided
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This alternate code was supposed to compile without warnings, however
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with modern compilers this is no longer the case.
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with modern compilers this is no longer the case so it will only cleanly compile
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with `-Wno-` options.
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### Alternate build:
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To compile this alternate version:
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```sh
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make alt
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```
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### Alternate use:
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Use `prog.alt` as you would `prog`.
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## Judges' remarks:
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One line, one array, one loop and one statement but it prints many bytes. It won.
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@@ -40,9 +50,9 @@ One line, one array, one loop and one statement but it prints many bytes. It won
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## Author's remarks:
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Feed this anything on stdin.
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Feed this anything on `stdin`.
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The [included script](scripthd) may be used as a driver program for this entry.
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The [included script.sh](scripthd.sh) may be used as a driver program for this entry.
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It adds several nice-to-have features, and allows salt-to-taste customizability.
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This code has been compiled and tested on:
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@@ -51,21 +61,24 @@ This code has been compiled and tested on:
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* X86-Linux, gcc 4.1.2 and 4.8.4, -O0 and -O3
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* ARM-QEMU, gcc 4.8.4, -O0 and -O3
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* X86-FreeBSD 10.3, clang 3.4.1, -O0 and -O3
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* TCC 0.9.26 (x86-64) (used as a proxy for [2001/bellard](http://ioccc.org/years.html#2001_bellard))
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* TCC 0.9.26 (x86-64) (used as a proxy for [2001/bellard](/years.html#2001_bellard))
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* UNIX V7 pcc (Johnson's C compiler) on a [simulated PDP-11/45](http://simh.trailing-edge.com/)
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(see spoiler for further detail)
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<div style="margin-bottom:60em;margin-top:4em"><strong>Spoiler below; scroll down.</strong></div>
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### SPOILER:
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This started life as a personal challenge: write the shortest hex dump utility in C.
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This started life as a personal challenge: write the shortest hex dump utility
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in C.
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The self-imposed ground rules in the hunt for shortest:
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- the code has to output correctly,
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- no extraneous newlines, the code must be portable,
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and without bypassing the solution using execve(2), or functions built upon it (system(3), popen(3), etc).
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- The code has to output correctly.
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- No extraneous newlines, the code must be portable,
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and without bypassing the solution using `execve(2)`, or functions built upon it
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(`system(3)`, `popen(3)`, etc).
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E.g:
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@@ -155,8 +168,10 @@ $
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```
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An obfuscated hex dump has been done before:
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[1986/bright/bright.c](http://ioccc.org/1986/bright/bright.c) is similar in function,
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but it uses more characters in just setting up its obfuscation than this entire solution!
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[1986/bright](/1986/bright/README.md) is similar in function,
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but it uses more characters in just setting up its obfuscation than this entire
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solution!
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### BIGGER SPOILER:
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@@ -165,12 +180,13 @@ replace the cryptic expression `4<(4^l>>5)?l:46` with `32>l|l>126?46:l`.
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Both take the same number of characters, but the former is a bit more interesting.
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Bonus question: how does the first expression work?
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### BIGGEST SPOILER (and some history):
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Technically, `char o[0];` is illegal (SS 6.7.6.2) according to ISO (N1570). And
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`char o[];` is a conditionally supported feature (SS 6.7.6.2, 6.10.8.3).
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However, it works in modern C implementations as an extension, including GCC,
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Clang and TCC, for X86 and ARM, on multiple operating systems (Linux, OSX,
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Clang and TCC, for X86 and ARM, on multiple operating systems (Linux, OSX/macOS,
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FreeBSD), so it is _functionally_ correct. MicroSoft Visual C++ does not allow
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`char o[]` or `char o[0]`, and implements its close relative `char o[1]` such
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that writing more than a single char will cause a fault, which is _technically_
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@@ -185,7 +201,8 @@ bytes following `O`, addressed via `o`, and this code only needs 17. This is
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_undefined_ behavior, but as shown, it is widely available.
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The [1979 Seventh Edition UNIX][1] (v7) system pre-dates the IOCCC by several years,
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and the source code to `sh`(1) was a [significant inspiration for this contest][2].
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and the source code to `sh`(1) was a [significant inspiration for this
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contest](/all/README.md).
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There are two C compilers present: `cc` written by Dennis Ritchie, and `pcc` written by Steven Johnson.
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The nested conditional expressions in 116 and smaller are too complex for `cc` ("Illegal conditional")
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but `pcc` handles them correctly, and neither compiler accepts `char o[]` or
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@@ -194,9 +211,9 @@ not yet written for UNIX).
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[1]: http://minnie.tuhs.org/cgi-bin/utree.pl
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[2]: http://ioccc.org/all/README
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[3]: https://web.archive.org/web/20180521074522/http://www.computerworld.com.au/article/279011/a-z_programming_languages_bourne_shell_sh/?pp=4
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[2]: https://web.archive.org/web/20180521074522/http://www.computerworld.com.au/article/279011/a-z_programming_languages_bourne_shell_sh/?pp=4
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More significant is that v7 `printf`(3) does not report the number of characters
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More significant is that v7 `printf(3)` does not report the number of characters
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written, and therefore 111 compiles but does not work correctly; 113 is the
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shortest code that compiles and runs correctly in Ancient UNIX.
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@@ -216,7 +233,7 @@ page 71, remarks:
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It is fascinating to explore the roots of C through the history of the operating
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system it was birthed within. C is often criticized as a difficult, inscrutable
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language, but as this contest demonstrates, this is in parody. _Shell-gol_ is
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one of those instances where someone [preferred a different language][3], and
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one of those instances where someone [preferred a different language][2], and
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(ab)used the preprocessor to re-mold C into something they found comfortable.
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Most of the rest of the system, especially in the kernel, are models of clarity
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and efficient expression.
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@@ -247,6 +264,12 @@ Try:
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cat prog.c prog.alt.c
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```
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or
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```sh
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cmp -b prog.c prog.alt.c
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```
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to compare the differences (`diff` is not helpful on a one-liner).
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File renamed without changes.
Executable
+39
@@ -0,0 +1,39 @@
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#!/usr/bin/env bash
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#
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# try.sh - demonstrate IOCCC winner 2018/burton1
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#
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# make sure CC is set so that when we do make CC="$CC" it isn't empty. Doing it
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# this way allows us to have the user specify a different compiler in an easy
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# way.
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if [[ -z "$CC" ]]; then
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CC="cc"
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fi
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make CC="$CC" everything >/dev/null || exit 1
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for i in prog scripthd.sh; do
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echo "$ ./$i < prog.c" 1>&2
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./"$i" < prog.c
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echo 1>&2
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read -r -n 1 -p "Press any key to run: ./$i < prog (space = next page, q = quit): "
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echo 1>&2
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./"$i" < prog | less -EXF
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echo 1>&2
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read -r -n 1 -p "Press any key to run: ./$i < scripthd.sh (space = next page, q = quit): "
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echo 1>&2
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./"$i" < scripthd.sh | less -EXF
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echo 1>&2
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read -r -n 1 -p "Press any key to run: head $0 | ./$i: "
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echo 1>&2
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head "$0" | ./"$i"
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echo 1>&2
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read -r -n 1 -p "Press any key to run: tail -n 15 Makefile | ./$i: "
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echo 1>&2
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tail -n 15 Makefile | ./"$i"
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done
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