Having problem with this pointer returning function

Question

I'm having some problems with a simple function call I'm trying to write; basically, the function takes a string and a character argument and returns a pointer to the first instance of that character in the string. The call in this instance uses a for loop to use pointers to strings to print out 4 strings. I've tried fiddling around with a bunch of things but can't get the function and call to work. Any help would be greatly appreciated.

#include <stdio.h>
#define NUMBER 4

char * strsrch(char * string, char x);
int main(void)
{
    char * ptr[NUMBER];
    int x;
    char * word[NUMBER] = {"This is string 1", "Now string 2", "Proceeding through string 3", "And then, the last string"};
    for(x = 0; x < NUMBER; x++)
        puts(word[x]);
    for(x = 0; x < NUMBER; x++)
        puts(strsrch(word[x], 'i'));


    return 0;
}

char * strsrch(char * string, char x)
{
    while (*string && (*string != x))
        string++;

    if (*string = x)
        return string;
    else
        return NULL;

}

Would abort during the .exe. Fixed now though.

Matt
– Matt

2011-08-07 02:23:22 +00:00
Commented Aug 7, 2011 at 2:23 — Matt
– Matt, Commented Aug 7, 2011 at 2:23

MByD · Accepted Answer · 2011-08-07 01:51:35Z

9

This if (*string = x) should be if (*string == x)

You assigned x to *string instead of comparing them .

answered Aug 7, 2011 at 1:51

MByD

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7 Comments

Matt Over a year ago

FUUUUUUUUUUU not again!! Thanks!

MByD Over a year ago

@Matt - the speed of answer indicates the number of time I did it :)

Greg Hewgill Over a year ago

@Matt: You really should turn up the warning level on your compiler, since all modern compilers will warn about that exact problem if you enable it.

hari Over a year ago

@Greg Hewgill: Is there a good read on enabling compiler warnings?

Matt Over a year ago

@Greg Hewgill: That's a good idea, will probably save me a lot of time, thanks!

|

MRAB · Accepted Answer · 2011-08-07 01:52:27Z

3

It should be:

if (*string == x)

answered Aug 7, 2011 at 1:52

MRAB

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Comments

phoxis · Accepted Answer · 2011-08-07 02:15:29Z

You have done if (*string = x) which will assign the character (value) of x into the location pointed by string , and if x is not 0 then this if will be always true. You wanted to compare the value of x and the first character of string which is done by if (*string == x) . This will compare the values.

To avoid such mistakes/typos, in such cases you can define the char * as constant to forbid accidental modification of the values which you do not want to be changed. For example in this case you can define your function like:

char * strsrch(const char * string, char x);

This will stop you from assigning the value of x into the string at the time of compilation.

Also you can use more warning level with your compiler. For example with gcc turning on -Wall will warn you about the assignment .

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