Deleting null character from a file

When writing in a file, I generate several null characters /00 each time a new write operation is performed. Bellow it is my approach to tackle this task, but it does not work.

File content:

foo\00\00\00\00\00\00

Code approach:

int aux;
while((aux = fgetc(fp)) != EOF){
    printf("%i\n", aux);
    if(fgetc(fp) == '\00'){
        fseek(fp, -1, SEEK_SET);
        ftruncate(fileno(fp), ftell(fp)); 
    }
}

How should this be done?