How to write an array to file in C

Question

I have a 2 dimensional matrix:

char clientdata[12][128];

What is the best way to write the contents to a file? I need to constantly update this text file so on every write the previous data in the file is cleared.

Answer 1

Since the size of the data is fixed, one simple way of writing this entire array into a file is using the binary writing mode:

FILE *f = fopen("client.data", "wb");
fwrite(clientdata, sizeof(char), sizeof(clientdata), f);
fclose(f);

This writes out the whole 2D array at once, writing over the content of the file that has been there previously.

Answer 2

I would rather add a test to make it robust ! The fclose() is done in either cases otherwise the file system will free the file descriptor

int written = 0;
FILE *f = fopen("client.data", "wb");
written = fwrite(clientdata, sizeof(char), sizeof(clientdata), f);
if (written == 0) {
    printf("Error during writing to file !");
}
fclose(f);