修改char * array [x] [y]

Question

How can I modify (increase ASCII value) each char in a two dimensional array of char * ?

I have this code now:

int riadky = 2;
int stlpce = 7;

char* x[riadky][stlpce];

int i,j;
for ( i = 0; i < riadky; i++)
    for (j = 0; j < stlpce; j++)
        x[i][j] = "test";

x[0][1] = "something";

for ( i = 0; i < riadky; i++){
    for (j = 0; j < stlpce; j++){
        printf("%s ", x[i][j]);
    }
        printf("\n");
}
printf("\n");

char * temp;
for ( i = 0; i < riadky; i++) {
    for (j = 0; j < stlpce; j++) {
        for (temp= x[i][j]; *temp; temp++) {
            (*temp)++;            //segmentation fault
        }
    }
}

When I run it, it segfaults on the line with the comment.

---

I try this, but still... segmentation falult

char ***alloc_array(int x, int y) {
    char ***a = calloc(x, sizeof(char **));
    int i;
    for(i = 0; i != x; i++) {
        a[i] = calloc(y, sizeof(char *));
    }
    return a;
}

int main() {

    int riadky = 3;
    int stlpce = 7;
    char ***x = alloc_array(riadky, stlpce);

    int i,j;
    for ( i = 0; i < riadky; i++){
        for (j = 0; j < stlpce; j++){
            strcpy(x[i][j],"asdasd");
        }
    }
    return 0;
}

Answer 1

 for ( i = 0; i < riadky; i++) for (j = 0; j < stlpce; j++) x[i][j] = "test"; x[0][1] = "something"; 

You are initializing your pointers to point to string literals. The compiler is allowed (but not required to) place string literals in read-only memory. An attempt to modify one of them is likely to result in a segmentation fault.

You need to allocate dynamic memory for your strings:

#include <stdlib.h>

...

for (...) {
  for (...) {
    x[i][j] = malloc (strlen (somestring)+1);
    if (x[i][j]) {
      strcpy (x[i][j], somestring);
    } else {
      /* Allocation error */
    }

where somestring is a string literal or a variable containing the string you want to store. If you later need to store larger strings, you will have to realloc() your pointers. Don't forget to free() your pointers when you are done using them.

I noticed that you have edited your post to include another attempt at the same problem, this time using dynamically allocated arrays rather than static arrays. But you still haven't allocated any memory for the actual strings, just an array of pointers. My answer should work unchanged for both versions of your code.