` By definition in mathematics, the Fibonacci Numbers are the numbers`

in the below sequence:

0,1,1,2,3,5,8,13,21,34,55,89,144, ......

By definition, the first two Fibonacci numbers are 0 and 1, and each

subsequent number is the sum of the previous two. Some sources omit

the initial 0, instead beginning the sequence with two 1s.

In mathematical terms, the sequence Fn of Fibonacci numbers is defi-

ned by the recurrence relation

Fn = Fn-1 + Fn-2,

with seed values

F0 = 0 and F1 = 1.

#### Iterative Method:

#!/bin/bash#!/bin/bash

# SCRIPT: fibo_iterative.sh

# USAGE: fibo_iterative.sh [Number]

# PURPOSE: Generate Fibonacci sequence.

# \\\\ ////

# \\ - - //

# @ @

# ---oOOo-( )-oOOo---

#

#####################################################################

# Script Starts Here #

#####################################################################

if [ $# -eq 1 ]

then

Num=$1

else

echo -n "Enter a Number :"

read Num

fi

f1=0

f2=1

echo "The Fibonacci sequence for the number $Num is : "

for (( i=0;i<=Num;i++ ))

do

echo -n "$f1 "

fn=$((f1+f2))

f1=$f2

f2=$fn

done

echo

**OUTPUT:**

# sh fibo_iterative.sh 18

The Fibonacci sequence for the number 18 is :

0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584

# sh fibo_iterative.sh

Enter a Number :20

The Fibonacci sequence for the number 20 is :

0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181 6765

#### Recursive Method:

#!/bin/bash

# SCRIPT: fibo_recursive.sh

# USAGE: fibo_recursive.sh [Number]

# PURPOSE: Generate Fibonacci sequence.

# \\\\ ////

# \\ - - //

# @ @

# ---oOOo-( )-oOOo---

#

#####################################################################

# Arguments Checking #

#####################################################################

if [ $# -eq 1 ]

then

Num=$1

else

echo -n "Enter a Number : "

read Num

fi

#####################################################################

# Define Functions Here #

#####################################################################

Fibonacci()

{

case $1 in

0|1) printf "$1 " ;;

*) echo -n "$(( $(Fibonacci $(($1-2)))+$(Fibonacci $(($1-1))) )) ";;

esac

#$(( )) construct is used instead of **expr** command for doing addition.

#$( ) constrict is used instead of back ticks.

}

#####################################################################

# Main Script Starts Here #

#####################################################################

echo "The Fibonacci sequence for the number $Num is : "

for (( i=0; i<=$Num; i++ ))

do

Fibonacci $i #Calling function Fibonacci

done

echo

**OUTPUT:**

# sh fibo_recursive.sh

Enter a Number : 11

The Fibonacci sequence for the number 11 is :

0 1 1 2 3 5 8 13 21 34 55 89

# sh fibo_recursive.sh 13

The Fibonacci sequence for the number 13 is :

0 1 1 2 3 5 8 13 21 34 55 89 144 233

Be aware that recursion is resource-intensive and executes slowly,

and is therefore generally not appropriate to use in a script.

[root@localhost shell]# time ./fibo_iterative.sh 15

The Fibonacci sequence for the number 15 is :

0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610

real 0m0.008s

user 0m0.008s

sys 0m0.000s

[root@localhost shell]# time ./fibo_recursive.sh 15

The Fibonacci sequence for the number 15 is :

0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610

real 0m7.875s

user 0m0.908s

sys 0m5.188s

Too many levels of recursion may crash a script with a segfault.

## Wednesday, December 22, 2010

Posted by venu k

14 comments | 12:38 PM

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Hi,

ReplyDeleteThanks for sharing. Just to share my own version too:

fibo() { local a=0; b="$1"; inc="$2"; while ((b < $inc)); do tmp=$((a+b)); a=$b; b="$tmp"; printf '%s ' "$tmp"; done; }; fibo 34 2000

Regards,

Valentin

Enter a Number :4

ReplyDeleteThe Fibonacci sequence for the number 4 is :

fib.sh: 27: fib.sh: Syntax error: Bad for loop variable

Copy/paste from here, no errors.

Shame on you!

ReplyDeletea=1;b=1;for i in `seq 91`;do echo $((x=b,b=a+b,a=x));done

That's all, folks!

Same thing, if you want to print also first numbers of sequence:

ReplyDeleteecho $((b=1,a=0));for i in `seq 92`;do echo $((x=b,b=a+b,a=x));done

Prints out Fibonacci numbers

ReplyDelete#include

int main()

{

int old_number= 1;

int current_number = 1;

int next_number;

while (current_number < 200) {

printf("%d\n", current_number);

next_number = current_number + old_number;

old_number = current_number;

current_number = next_number;

}

return (0);

}

To include commas in the output:

ReplyDeleteecho -n "$f1 " | sed -r ':L;s=\b([0-9]+)([0-9]{3})\b=\1,\2=g;t L'

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