copy strings in array

hi,

i have a string printed to by sprintf. i would like to: for every string printed, it copies the contents into the next element of a char array:

something like this (but this dosent work...

Code:

---

#include <stdio.h>
#include <string.h>

void addchars(char *sa[]){

int i;
char buf[100];

 for(i = 0; i  <= 3; ++i){
  sprintf(buf, "david %d\n",i);
  printf("%s", buf);
  strcpy(&sa[i],buf);
 }
}



int main() {

char *sa[25];


printf ("%s\n",sa[0]);
addchars(sa);
//printf("%s,%s,%s,%s,%s\n",sa[0],sa[1],sa[2],sa[3],sa[4]);
printf("%s",sa[0]);

return 0;


}

---

thanks

As you have been told, sa is an array of pointers, which are uninitialized. Pointers are not a storage unit.
And trying to print the contents from an uninitialized pointer will undoubtedly cause a crash right away.
http://cpwiki.sourceforge.net/Common...kes_and_errors

First off, you have to decide what this:

Quote:

---

for every string printed, it copies the contents into the next element of a char array:

---

means. By definition, you cannot get a string into the next element of a char array -- the only thing you can get into the next element of a char array is a char.

Now, since you don't have any char arrays in your code, but do have char * arrays, I assume you mean that. In that case, sa[0], sa[1], ... are already your char *s that you would want to copy to, so adding & is fruitless. HOWEVER: currently sa[0], sa[1], etc. point to somewhere in New Jersey. You need to make them point to a string inside your computer, usually using malloc.

sorry :s

so: i have to make char * sa point to a space resevered by malloc?

-> is it even possible to get sa[0] = david 1, sa[1] = david 2 etc?

thanks for the quick response...

Yes, or just make them allocated on the stack.
There are several ways to assign values to arrays, depending on what you need.
If you need string literals (non-modifiable), assign a string literal to a const char* pointer.
If you need a modifiable buffer, then create a buffer and use strcpy.

so like malloc(sizeof(sa)); ?

im not gonna lie anymore - i suck at string manipulation... i dont know how i would do that...

Quote:

---

Originally Posted by davo666

sorry :s

so: i have to make char * sa point to a space resevered by malloc?

-> is it even possible to get sa[0] = david 1, sa[1] = david 2 etc?

thanks for the quick response...

---

You need to make each element of sa point to space reserved by malloc (not the array itself, but each string in the array).

If you would kindly state exactly what you want.
Do you want to, for example, copy the contents of element 0 into 1, etc, until the end of the array?

no, i want to make a string with sprintf , then put that string into the first element of an array passed from the main function, then on the second iteration the second element.

thanks

@tabstop: ooooh so i initialise sa[i] = malloc(sizeofmystringfromsprintf); then make that space equal buf?

im going to try that :)

Code:

---

char sa[SUFFICIENT_SPACE_HERE][25];

---

Boom! Your program should work (well almost), except for the printf in the beginning which tries to print an unexisting string.

umm:

Code:

---

include <stdio.h>
#include <string.h>

void addchars(char sa[]){

int i;
char buf[100];

 for(i = 0; i  <= 3; ++i){
  sprintf(buf, "david %d\n",i);
  printf("%s", buf);
  strcpy(sa[i],buf);
 }
}



int main() {

char sa[128][25];



addchars(sa);
printf("%s",sa[0]);

return 0;


}

---

this revised code dosent work...

Well, what the heck happened to "char *sa[]"? Edit: Even better yet, why not make it char sa[128][25]?

sorry, i used an old version of addchars, and copied the new main...

Code:

---

void addchars(char *sa[]){

int i;
char buf[100];

 for(i = 0; i  <= 3; ++i){
  sprintf(buf, "david %d\n",i);
  printf("%s", buf);
  strcpy(sa[i],buf);
 }
}



int main() {

char sa[128][25];



addchars(sa);
printf("%s",sa[0]);

return 0;


}

---

still doesn't work: test.c: In function 'main':
test.c:24: warning: passing argument 1 of 'addchars' from incompatible pointer type

thanks for all your help though

You'll need at least the 25 in the function declaration.

i still get the error msg though...

So you can do either

Code:

---

void addchars(char sa[128][25])

---

or

Code:

---

void addchars(char (*sa)[25])

---

at your convenience.

thankyou,

it seems like i need a mega c tutorial rehash on pointers and arrays!

thanks for your time.

it looks like you need to learn to differentiate between pointers and arrays, since they can be very similar but very different at the same time.