Fibonacci Number Generator (src)

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  • DevynCJohnson
    • Topics - 437
    • @devyncjohnson

    "fib" (Fibonacci Number Generator) is a fast and cross-platform program that can be used to find a Fibonacci number. This small program works in a command-line and can be called in shell-scripts. Currently, the program cannot find Fibonacci numbers beyond the 410th Fibonacci number. "fib" (Fibonacci Number Generator) is licensed under LGPLv3 and is made by Devyn Collier Johnson <[email protected]>.

    NOTE: "fib" has been merged with "Linux-Utils" ( Updates will be released with Linux-Utils rather than this page.

    To compile the C-source-code, execute one of the below listed commands. Suggestions for other compiler commands are welcome.

    • General (GNU GCC) - gcc -O3 -gtoggle -g0 -s -pipe -pedantic -std=c11 ./fib.c -o ./fib
    • Optimized (GNU GCC) - gcc -O3 -gtoggle -g0 -s -pipe -funroll-loops -ffunction-sections -fdata-sections -std=c11 -Wl,-O3 ./fib.c -o ./fib && strip --remove-section=.note --remove-section=.comment --strip-debug --strip-unneeded ./fib

    To use the program, in a terminal, type "/PATH/TO/fib 10" to get the tenth Fibonacci number.

    Please feel free to email me suggestions, bug reports, concerns, etc. Also, please consider donating to DCJTech for further development.


    Download Version 2015.11.15

    Source Code

    Created by Devyn Collier Johnson
    <[email protected]>
    GNU Lesser General Public License v3
    Copyright (c) Devyn Collier Johnson, All rights reserved.
    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 3.0 of the License, or (at your option) any later version.
    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    Lesser General Public License for more details.
    You should have received a copy of the GNU Lesser General Public
    License along with this library.
    // gcc -O3 -gtoggle -g0 -s -pipe -pedantic -std=c11 ./fib.c -o ./fib
    // gcc -O3 -gtoggle -g0 -s -pipe -funroll-loops -ffunction-sections -fdata-sections -pedantic -Wall -Wextra -std=c11 -Wl,-O3 ./fib.c -o ./fib && strip --remove-section=.note --remove-section=.comment --strip-debug --strip-unneeded ./fib
    // Fibonacci Number Generator
    // Usage: ./fib 10  # Return the tenth Fibonacci number
    #include <stdio.h>
    #include <stdlib.h>
    #if defined(__linux__)
    #if !defined(_GNU_SOURCE)
    #define _GNU_SOURCE
    #include <unistd.h>
    #elif !defined(_WIN32) && (defined(__unix__) || defined(__unix) || (defined(__APPLE__) && defined(__MACH__)))
    #define _POSIX_C_SOURCE = 199309L
    #include <unistd.h>
    #if defined(__unix__) || (defined(__APPLE__) && defined(__MACH__))
    #include <sys/param.h>
    #if defined(BSD)
    // static const char __author__[32] = "Devyn Collier Johnson";
    // static const char __copyright__[8] = "LGPLv3";
    // static const char __version__[16] = "2015.11.15";
    unsigned int fib(const unsigned int num);
    unsigned int fib(const unsigned int num) {
        // Fibonacci Number Generator
        unsigned int i;
        unsigned int fval[num+1];
        if (num > 410) {
            printf("ERROR! Number too large.\n");
            return 0;
        } else {
            if (num == 0) {
                return 0;
            } else if (num == 1 || num == 2) {
                return 1;
            } else {
                fval[0] = 0;
                fval[1] = 1;
                fval[2] = 1;
                fval[3] = 2;
                fval[4] = 3;
                for (i = 2; i <= num; i++) {
                    fval[ i ] = fval[ i - 1 ] + fval[ i - 2 ];
                return fval[num];
    int main(int argc, char *argv[]) {
        printf("%u\n", fib((unsigned int) strtol(argv[1], (char **)NULL, 10)));
        return 0;


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