C language: try to implement IndexOf function - c

Question

I try to learn C Language and something is not clear to me.
I want to write IndexOf function that search for char inside string and return the Index number.
I am running this under ubuntu and compile using this:
test1: test.c
gcc -g -Wall -ansi -pedantic test.c -o myprog1
This is what i have try:
int c;
int result;
printf("Please enter string: ");
scanf("%s", str1);
printf("Please enter char: ");
scanf("%d", &c);
result = indexof(str1, c);
printf("Result value: %d\n", result);
And this is my function:
int indexof(char *str, int c)
{
int i;
for (i = 0; i < strlen(str); i++)
{
if (str[i] == c)
return i;
}
return -1;
}
So my problem is that my function return -1 all the time

Answer 1

scanf("%c",&c)..you are getting input a character.
Working copy would besomethign like:-
char c; // you want to find the character not some integer.
int result;
printf("Please enter string: ");
scanf("%s", str1);
printf("Please enter char: ");
scanf("%d", &c);
result = indexof(str1, c);
printf("Result value: %d\n", result);
Working example:-
#include <stdio.h>
#include <string.h>
int indexof(char *str, char c)
{
int i;
for (i = 0; i < strlen(str); i++)
{
if (str[i] == c)
return i;
}
return -1;
}
int main()
{
char c;
int result;
char str1[100];
printf("Please enter string: ");
scanf("%s", str1);
printf("Please enter char: ");
scanf(" %c", &c);
result = indexof(str1, c);
printf("Result value: %d\n", result);
}

Answer 2

Since c is int:
int indexof(char *str, int c)
{
int i;
for (i = 0; i < strlen(str); i++)
{
if ((str[i]-'0') == c) // convert char to int
return i;
}
return -1;
}

Answer 3

write IndexOf function that search for char inside string and return the Index number.
You might like to have a look at the strchr() function, which can be used as shown below:
/* Looks up c in s and return the 0 based index */
/* or (size_t) -1 on error of if c is not found. */
#include <string.h> /* for strchr() */
#include <errno.h> /* for errno */
size_t index_of(const char * s, char c)
{
size_t result = (size_t) -1; /* Be pessimistic. */
if (NULL == s)
{
errno = EINVAL;
}
else
{
char * pc = strchr(s, c);
if (NULL != pc)
{
result = pc - s;
}
else
{
errno = 0;
}
}
return result;
}
You could call it like this:
size_t index_of(const char *, char);
#include <stdlib.h> /* for EXIT_xxx macros */
#include <stdio.h> /* for fprintf(), perror() */
#include <errno.h> /* for errno */
int main(void)
{
result = EXIT_SUCCESS;
char s[] = "hello, world!";
char c = 'w';
size_t index = index_of(s, 'w');
if ((size_t) -1) == index)
{
result = EXIT_FAILURE;
if (0 == errno)
{
fprintf("Character '%c' not found in '%s'.\n", c, s);
}
else
{
perror("index_of() failed");
}
}
else
{
fprintf("Character '%c' is at index %zu in '%s'.\n", c, index, s);
}
return result;
}