Question

i want to open a file, write some data on it so i have to use (Fopen) ” i can’t use open because i need fopen in some other things ”

now if i want to write on the file using fwrite it just don’t i don’t know why this is what i referred to in my code #option1, but if i get the file descriptor and use normal write method everything works fine see #option 2 below.

anyone can help me to make fwrite works ?

    char file_data[256] // has some values 
    int file_size = strlen(file_data);
    FILE *file;
    file = fopen(MY_FILE_NAME, "w+");


    if(!file){//edited 
           return false;
    }


    #option 1//this is not working 
    fwrite(file_data,1,file_size,file);
    #end of option 1

    #option 2//this works 
    int fd = fileno(file);
    int x = write(fd,file_data,file_size);//
    #end of option 1

EDIT

my file_data is something like this

1. 4 bytes is reserved for an integer (required)
2. 200 bytes is reserved for a string (optional)

Answer 1

buffered IO operations use a buffer that is managed by the C lib. Your “problem” is that fwrite is buffered meaning that in order to write to the file you most likely need to flush it with fflush() or just close the file.