Passing function as argument in C

#include <stdio.h>
int add(int, int);
int sub(int, int);
int mul(int, int);
int div(int, int);
int myfunPtr(int , int , int(*)(int, int));
 
int add(int var1, int var2)
{
 return var1 + var2;
}
 
int sub(int var1, int var2)
{
 return var1 - var2;
}
 
int mul(int var1, int var2)
{
 return var1 * var2;
}
 
int div(int var1, int var2)
{
 return var1 / var2;
}
int myfunPtr(int a, int b, int(*argFun)(int, int))
{
 int x = 0;
 x = (*argFun)(a, b);
 return x;
}
 
int main(int argc, char **argv)
{
 int x = 0;
 x = myfunPtr(100, 5, add);
 printf("o/p : %d\n", x);
 
 x = myfunPtr(100, 5, sub);
 printf("o/p : %d\n", x);
 
 x = myfunPtr(100, 5, mul);
 printf("o/p : %d\n", x);
 
 x = myfunPtr(100, 5, div);
 printf("o/p : %d\n", x);
 
 return 0;
}

Function table in C

#include <stdio.h>
int add(int, int);
int sub(int, int);
int mul(int, int);
int div(int, int);
 
int add(int var1, int var2)
{
    return var1 + var2;
}
 
int sub(int var1, int var2)
{
        return var1 - var2;
}
 
int mul(int var1, int var2)
{
        return var1 * var2;
}
 
int div(int var1, int var2)
{
        return var1 / var2;
}
 
int main(int argc, char **argv)
{
        int (*fun_table[4]) ();
        int result = 0;
        
        fun_table[0] = add;
        fun_table[1] = sub;
        fun_table[2] = mul;
        fun_table[3] = div;
        
        result = (*fun_table[0])(100, 5);
        printf("add : %d\n", result);
        
        result = (*fun_table[1])(100, 5);
        printf("sub : %d\n", result);
        
        result = (*fun_table[2])(100, 5);
        printf("mul : %d\n", result);
        
        result = (*fun_table[3])(100, 5);
        printf("div : %d\n", result);
        
        return 0;
}

Function pointer in C

One pointer variable can point to another variable. 

Similarly one function can point another function. 

This method is helped in callback mechanism. i,e) passing function as argument to anther function.

#include <stdio.h>
int add(int, int);
 
int add(int var1, int var2)
{
 return var1 + var2;
}
 
int main(int argc, char **argv)
{
 int x = 0;
 int (*functionPtr)(int, int);
 functionPtr = &add;
 x = (*functionPtr)(10, 15);
 printf("%d\n", x);
 return 0;
}

Shell script to check Armstrong number

SCRIPT:

#!/bin/bash
echo -n "Enter the nuber : "
read read_val
number=$read_val
buf1=0
buf2=0
sum=0
while [ $number -gt 0 ]
do
    buf1=`expr $number % 10`
    buf2=`expr $buf1 \* $buf1 \* $buf1`
    sum=`expr $sum + $buf2`
    number=`expr $number / 10`
   
done
if [ $sum -eq $read_val ]
then
    echo "$read_val is armstrong number"
else
    echo "$read_val not a armstrong number"
fi

OUTPUT:
(i)
Enter the nuber : 178
178 not a armstrong number
(ii)
Enter the nuber : 178
178 not a armstrong number


   

Shell script to find factorial of an number

SCRIPT:

#!/bin/bash
input=$1
fact_op=1
while [ $input -gt 0 ]
do
    echo "$fact_op  $input"
    fact_op=$(( $fact_op * $input ))
    input=$(( $input - 1 ))
done
echo "factorial of value $1 is $fact_op"

OUTPUT:
sujin@sujin:~/work/shell$ ./factorial.sh 5
1  5
5  4
20  3
60  2
120  1
factorial of value 5 is 120