Binary files printing and desired precision
- by yCalleecharan
Hi, I'm printing a variable say z1 which is a 1-D array containing floating point numbers to a text file so that I can import into Matlab or GNUPlot for plotting. I've heard that binary files (.dat) are smaller than .txt files. The definition that I currently use for printing to a .txt file is:
void create_out_file(const char *file_name, const long double *z1, size_t z_size){
FILE *out;
size_t i;
if((out = _fsopen(file_name, "w+", _SH_DENYWR)) == NULL){
fprintf(stderr, "***> Open error on output file %s", file_name);
exit(-1);
}
for(i = 0; i < z_size; i++)
fprintf(out, "%.16Le\n", z1[i]);
fclose(out);
}
I have three questions:
Are binary files really more compact than text files?;
If yes, I would like to know how to modify the above code so that I can print the values of the array z1 to a binary file. I've read that fprintf has to be replaced with fwrite. My output file say dodo.dat should contain the values of array z1 with one floating number per line.
I have %.16Le up in my code but I think that %.15Le is right as I have 15 precision digits with long double. I have put a dot (.) in the width position as I believe that this allows expansion to an arbitrary field to hold the desired number. Am I right? As an example with %.16Le, I can have an output like 1.0047914240730432e-002 which gives me 16 precision digits and the width of the field has the right width to display the number correctly. Is placing a dot (.) in the width position instead of a width value a good practice?
Thanks a lot...
