beef

penetration testing tool that focuses on the web browser

SYNOPSIS

beef [OPTION]... FILE

DESCRIPTION

Beef is a flexible interpreter for the Brainfuck programming language.

It can be configured using the options described below, making it possible to run Brainfuck programs that make assumptions about the behavior of the interpreter.

Beef sets no arbitrary limit to the size of the memory tape used by the program, and allocates memory cells as they are needed.

OPTIONS

-p, --program=PROGRAM

Execute PROGRAM. This can only be used if a FILE containing a Brainfuck program has not been provided on the command line after all options.

-s, --store=WHAT

Choose the value to store in the tape when the end of input is reached. WHAT defaults to zero (store a zero); other possible values are eof (store -1, the value usually assigned to the C constant EOF) or same (leave the value untouched).

-d, --enable-debugging

Enable debugging support. By default, debugging instructions are not executed.

-o, --output-file=FILE

Write program's output to FILE.

-i, --input-file=FILE

Read program's input from FILE.

FILE can be local path or any URI supported by GIO. If FILE is '-', standard input or standard output, depending on the context, will be used.

BRAINFUCK LANGUAGE

Brainfuck programs work on a memory tape which contains a virtually unlimited number of cells; each cell can store a value, which can be seen either as a character or as an integer number (its ASCII encoding) depending on the context. There is a cursor pointing to one of the cells, which is considered to be the current one; the cursor can be moved around at will.

A Brainfuck source file is made of a number of Brainfuck instructions; any symbol which is not an instruction is considered a comment and is ignored. There are exceptions to this rule, see below.

The Brainfuck instructions are:

+

Increase the value in the current cell by one.

-

Decrease the value in the current cell by one.

>

Move the cursor one cell to the right.

<

Move the cursor one cell to the left.

[

Start a loop. The instructions contained in the loop are executed as long as the value of the current cell is not zero.

]

End a loop started by a '[' instruction.

,

Read a character from the input and store it in che current cell.

.

Write the value of the current cell to the output.

#

Dump the content of the memory tape for debugging purposes. This instruction is ignored unless the enable-debugging option is present.

If the first line of the source file starts with the magic sequence '#!' it is ignored. This allows you to execute a Brainfuck program without calling Beef explicitly, like you would do for eg. a Python program.

The symbol '!' has a special meaning to Beef: it marks the end of a program's code and the beginning of its input. If this symbol is present in the source file, runtime input will be ignored.

EXAMPLES

The classic Hello World program could be written in Brainfuck as

++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++.>+.++++++
+..+++.>++.<<+++++++++++++++.>.+++.------.--------.>+.>.

The following Brainfuck program can be used to replace the cat(1) utility:

#!/usr/bin/beef
,[.,]

That's of course assuming you don't need any of cat(1)'s fancy commandline options, you have a shell with working I/O redirection and a sense of humor.

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