# C program to find sum of two numbers using command line arguments

Learn: How to find the sum of two integer numbers using command line arguments? Here, values will be given through the command line.

As we have discussed in command line argument tutorial, that we can also give the input to the program through the command line.

In this program, we will provide the input (two integer values) through the command line and program will add them and print the value of input numbers along with the sum of them.

Sample input

`./main  10  20`

Here, ./main is the program's executable file name, 10 and 20 are the input values.

Sample output

`Sum of 10, 20 is: 30`

## Program to find the sum of two integer numbers using command line arguments in C

```#include <stdio.h>

int main(int argc, char *argv[])
{
int a,b,sum;
if(argc!=3)
{
printf("please use \"prg_name value1 value2 \"\n");
return -1;
}

a = atoi(argv);
b = atoi(argv);
sum = a+b;

printf("Sum of %d, %d is: %d\n",a,b,sum);

return 0;
}
```

Output

```First run:
sh-4.2\$ ./main 10 20
Sum of 10, 20 is: 30

Second run:
sh-4.2\$ ./main 10 20 30 40
please use "prg_name value1 value2 "
```

### What is atoi()?

atoi() is a library function that converts string to integer, when program gets the input from command line, string values transfer in the program, we have to convert them to integers (in this program). atoi() is used to return the integer of the string arguments.

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