C Programming: store getchar as a char array

Question

I am working on a program that receives an input from the user stores it as a string of digits (assume no faulty input) and converts this char string/array back into an integer. I realize I could just store the input as an integer originally but I am trying to practice some conversion methods.

Currently my error involves the function atoi(), which has a "conflicting types" received message.

#include <stdio.h>
#include <stdlib.h>

int atoi(char s[])
{
    int i, n;

    n = 0;
    for (i = 0; s[i] >= '0' && s[i] <= '9'; ++i)
    {
        n = 10 * n + (s[i] - '0');
    }
    return n;
}

int main(void)
{
    char str[5];
    int c, i;

    printf("Please enter a number");
    for (i = 0; (c = getchar()) != '\n'; ++i)
    {
        str[i] = c;
    }
    printf("%d", atoi(str));
    return EXIT_SUCCESS;
}

Here is the error code:

Invoking: GCC C Compiler

gcc -O0 -g3 -Wall -c -fmessage-length=0 -MMD -MP -MF"src/Chapter2.d" -MT"src/Chapter2.d" -o "src/Chapter2.o" "../src/Chapter2.c"
../src/Chapter2.c:50:5: error: conflicting types for ‘atoi’
 int atoi(char s[])

I don't see you terminating the string anywhere. The random memory after the string might just contain legal digits. Also, if user enters more than 5 digits you may segfault. — Lee Daniel Crocker
– Lee Daniel Crocker, Commented Jan 5, 2015 at 17:47
Conflicting types error indicates you have multiple definitions for atoi. — Fiddling Bits
– Fiddling Bits, Commented Jan 5, 2015 at 17:49
the atoi() is a function in prototyped in one of the header files you included. Your implementation has a different prototype. This is a very good reason to call your functions by different names that those 'system' functions. For instance, if you called it 'myAtoi()' the problem would go away. — user3629249
– user3629249, Commented Jan 5, 2015 at 21:07

Gopi · Accepted Answer · 2015-01-05 17:51:59Z

3

atoi() is there in the standard library #include<stdlib.h> change your function name to something else

answered Jan 5, 2015 at 17:51

Gopi

19.9k4 gold badges28 silver badges37 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

C Programming: store getchar as a char array

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related