dynamically allocated strings??

Ok, part of my assignment for school is to create a struct with 2 char pointers in it. These pointers are supposed to point to a couple of dynamically allocated strings and I'm supposed to create a little function that prints the contents of the struct out. So far I have the struct:

Code:

---

typedef struct
{
        char *name;
        char *number;
}myStruct;

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And I have the print function:

Code:

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void printMyStruct(myStruct *a, myStruct *b)
{
    printf("%s: %s\n", *(a).name, *(b).number);
}

---

I think those two parts are right. My question is about the dynamically allocated strings that the pointers in my struct are supposed to point to. I'm not quite sure of how to do that..

Use the malloc() function.

For example:

Code:

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char *string = malloc(sizeof(char) * 100);

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. . . for a string of a size of 100 characters.

EDIT: don't forget to free the memory when you're done with it . . .

second part is wrong . has precedence over the * so it should not even compile

should be

printf("%s: %s\n", a->name, b->number);

to allocate string use malloc

Code:

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a->name = malloc(strlen(temp)+1);
if(a->name)
    strcpy(a->name,temp);

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I thought that's what it was but I wasn't sure because the instructions say that the strings shouldn't have any wasted space.. So, is it ok to do something like this?

Code:

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int capacity = 1;
int size = 0;
int c;
char *string = malloc(sizeof(char) * capacity);
while((c = fegetc(stdin) != EOF)
{
    string[size++] = c;
    if(size == capacity)
    {
          string = realloc ( string ,capacity * sizeof (char));
    }

---

Yes, it is, but be careful, because realloc() and malloc() can fail . . .

Right. I didn't include any code to check if they return NULL. I know I should for my program though. In the code I just posted I used fgetc(). Would it be possible to substitute fgets() instead?

Hmm. Yes, it is possible, but it would be quite useless, as you'd be using it in the same position as fgetc() unless you read into a huge temporary buffer.

Cool. Thank you. I'll post again if I run into any problems

Quote:

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Code:

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char *string = malloc(sizeof(char) * 100);

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. . . for a string of a size of 100 characters.

---

You meant 99?

Yes, yes, I'm sorry. My brain's on holidays tonight.

A string of 100 including the NULL, is what I meant . . .

Ok. One quick, little question. How do I get one of the pointers in my struct to point to the string??

Like so . . .

Code:

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a->name = localstring;

---

. . . for example. localstring is the malloc'd char *.

Hmm.. that's how I was trying to do it but I keep getting this error when I try to compile:

error: invalid type argument of ‘->’

Quote:

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Originally Posted by CS_Student8337

I thought that's what it was but I wasn't sure because the instructions say that the strings shouldn't have any wasted space..

---

in this case - use temporary static buffer to enter string and after that use strlen to detrmine the needed space to be allocated like in my example

Quote:

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Originally Posted by CS_Student8337

Hmm.. that's how I was trying to do it but I keep getting this error when I try to compile:

error: invalid type argument of ‘->’

---

is a pointer or struct?

Post the line you are getting that error message on, then we might be able to help you.

Or at least, vart will be able to, since I'm going to sleep now. ;)

Good luck.

Quote:

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Originally Posted by vart

in this case - use temporary static buffer to enter string and after that use strlen to detrmine the needed space to be allocated like in my example

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Were aren't allowed to use buffers in the assignment for some reason

Here's the line:

Code:

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aStruct->name = string;

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Quote:

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Originally Posted by CS_Student8337

Here's the line:

Code:

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aStruct->name = string;

---

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you need to add another line - where the aStruct is defined