Can size of an array be changed at runtime ? "C"

CPallini is right, but a better approach would be to use malloc to allocate the array, since that will place it on the heap instead of the stack.

Arrays can get very large, very quickly - and stack space is limited, usually about than 1MB where the heap can be "as much as your system will allow".

char** select = (char**) malloc (nr * sizeof(char*));

You can then use it as an array of strings without any problems. Remember to free the memory when you are finished with it!

This also has the advantage of persistence: if the array is declared directly within a function, then the stack space is freed up when the function returns, so the string pointers array cannot be used or returned from the function.

Okay now I understand.. I have one more question if I may ask. If I read lines from a text.txt file like this:

#include <stdio.h>

int main()
{
    FILE *file = fopen("text.txt", "r");
    char buffer[256] = {};
    unsigned int nr = 0;

    while(fgets(buffer, sizeof buffer, file) != NULL)
    {
        nr++;
    }

    char *select[nr]; // is this valid as well ?
    ...
    ..
    .
    fclose(file);
}

Can this be done as well ?