C parsing a string into an array of strings-CodePudding

While defining an array of strings, I usually declare it similar to the following:

    char *arr[5] =
{
    "example0",
    "example1",
    "example2",
    "example3",
    "example4"
};

Where I'm having a problem is I don't know how to pass a variable into one of the elements of arr.

For instance,

char str[6] = "1.0.0.1";

char *arr[6] =
{
    "example0",
    "example1",
    "example2",
    "example3 %s", str,
    "example4"
};

Of course, this doesn't work, it's just a basic illustration of what I'm having trouble with.

I also know I can later use strncat() or even snprintf() but, to avoid the pain of handling memory with those, I just want to know if parsing a variable into one of the strings of the array is possible at declaration.

CodePudding user response：

... if parsing a variable into one of the strings of the array is possible at declaration.

At compile time, could concatenate as below:

#define STR "1.0.0.1"
char str[] = STR;

char *arr[6] = { 
    "example0",
    "example1",
    "example2",
    "example3" " " STR, // Forms "example3 1.0.0.1"
    "example4"
};

Perhaps OP is interested in something formed during run-time. It uses a variable length array (VLA).

void foobar(const char *str) {
  int n = snprintf(NULL, 0, "example3 %s", str);
  char a[n]; // VLA.
  snprintf(a, sizeof a, "example3 %s", str);

  char *arr[6] = {
      "example0",
      "example1",
      "example2",
      a,
      "example4"
  };

  printf("<%s>\n", arr[3]);
}

int main(void) {
  foobar("1.0.0.1");
}

Output

<example3 1.0.0.>

Alternatively the space for the string could have been done via an allocation.

char *a = malloc(n   1u);
sprintf(a, "example3 %s", str);
....
free(a);