C atoi() function

C atoi() function - Convert a string to an integer

The atoi() function is used to convert a character string to an integer value.

Syntax:

int atoi(const char *str)

Parameters:

Return value from atoi()

• Returns an integer value that is produced by interpreting the input characters as a number.
• If the function cannot convert the input to a value of that type return value is 0.
• The return value is undefined in the case of an overflow.

Example: atoi() function

The following example shows the usage of atoi() function.

#include <stdlib.h>
#include <stdio.h>
 
int main(void)
{
    int in_val;
    char *s;
    s = " -4938";
    printf("String value: %s",s);
    in_val= atoi(s); 
    printf("\nInteger value = %d\n",in_val);
    s = "+4938";
    printf("\nString value: %s",s);
    in_val= atoi(s); 
    printf("\nInteger value = %d\n",in_val);
    s = "4938";
    printf("\nString value: %s",s);
    in_val= atoi(s); 
    printf("\nInteger value = %d\n",in_val);
    s = "0038";
    printf("\nString value: %s",s);
    in_val= atoi(s); 
    printf("\nInteger value = %d\n",in_val);
    s = "003800";
    printf("\nString value: %s",s);
    in_val= atoi(s); 
    printf("\nInteger value = %d\n",in_val);
}

Output:

String value:  -4938
Integer value = -4938

String value: +4938
Integer value = 4938

String value: 4938
Integer value = 4938

String value: 0038
Integer value = 38

String value: 003800
Integer value = 3800

C Programming Code Editor:

Previous C Programming: C atof()
Next C Programming: C atol()