Pointer as parameter is null but after function pointer is not null [duplicate]

Question

hello i have my funcion like:

void enterString(char *string) {

    string = (char*)malloc(15);

    printf("Enter string: ");
    scanf("%s",string); //don't care about length of string now
}

int main() {
   char *my_string = NULL;
   enterString(my_string);

   printf("My string: %s\n",my_string); /* it's null but i want it to 
                                          show string i typed from 
                                           enterString */

   return 0;
}

I want to string from function show on string in main ... I don't know if you'll understand me. Thank you :)

Quentin · Accepted Answer · 2014-06-02 13:55:03Z

3

You are passing string by value. You neet to pass it by address :

void enterString(char **string) {

    *string = (char*)malloc(15);

    printf("Enter string: ");
    scanf("%s",*string); //don't care about length of string now //you should!
}

int main() {
   char *my_string = NULL;
   enterString(&my_string);

   printf("My string: %s\n",my_string);

   free(my_string);

   return 0;
}

edited Jun 2, 2014 at 13:55

answered Jun 2, 2014 at 12:35

Quentin

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12 Comments

Quentin Over a year ago

Care to argument the downvote ?...

this Over a year ago

Why would I have to argument the downvote?

Quentin Over a year ago

So I can know what is wrong with my answer and improve it for everyone's gain. That's what this site is all about, right ?

Quentin Over a year ago

I was asking that in hope that the person having cast the downvote would see it and answer accordingly. Don't take it personally if it wasn't you :p

Quentin Over a year ago

You may want to double-check that comment, string is a char** ;)

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