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

Shell script to check file executable permission availability

SCRIPT:

#!/bin/bash
USAGE="usage : $0 {filename}"
CHECK_FILE=$1
if [ $# -lt 1 ]
then
 echo "$USAGE"
 exit 1
fi
if [ -x "$CHECK_FILE" ]
then
 echo "$CHECK_FILE has the executable permission"
else
 echo "$CHECK_FILE not has executable permission"
fi

OUTPUT-1:
test.sh has the executable permission

OUTPUT-2:
sujin_sr not has executable permission

C Program Lab Exercise

I. SWAPPING OF TWO NUMBERS USING FUNCTION:

Program:

#include <stdio.h>
void swap(int, int);
int main()
{
    int x, y;
    x = 10;
    y = 20;
    swap(x, y);
    printf("Value of x and y after swap(x, y) in main()  : %d %d \n", x, y);
}

void swap(int a, int b)
{
    int t;
    printf("Value of a and b before exchange in swap()   : %d %d \n", a, b);
    t = a;
    a = b;
    b = t;
    printf("Value of a and b after exchange in swap()    : %d %d \n", a, b);

    return 0;
}

Output:

Value of a and b before exchange in swap()   : 10 20
Value of a and b after exchange in swap()    : 20 10
Value of x and y after swap(x, y) in main()  : 10 20