How to change output from binary to ascii?

Question

I want to make a small change in one C code,in order to double-check some results.Just few relevant lines

 FILE           *f1_out, *f2_out;

/* open files */
if ((f1_out = fopen(vfname, "w")) == (FILE *) NULL)
{
   fprintf(stderr, "%s: Can't open file %s.\n", progname, vfname);
   return (-1);
}

Then goes some calculations and

yes = fwrite(vel, nxyz*sizeof(float), 1, f1_out);

How to change the last line to get the ascii output?

Note that if you open file for writing in binary mode, mode argument should be `"wb"`. Also, casting `NULL` with `(FILE *)` is unnecessary. — user694733, Apr 28 '16 at 12:05

score 2 · Answer 1 · answered Apr 28 '16 at 12:03

Assuming that your vel is an array of floats, and your nxyz is the number of floats in that array, and that you want the output on the standard output and not on the file you opened:

for (int i = 0; i < nxyz; ++i) {
    printf("vel[%d] = %f\n", i, vel[i]);
}

score 1 · Accepted Answer · answered Apr 28 '16 at 12:03

1

Instead of yes = fwrite(vel, nxyz*sizeof(float), 1, f1_out);, use

for(i = 0; i < nxyz; ++i) {
  yes &= (fprintf(f1_out, "%d:\t%f\n", i, vel[i]) > 0);
}

answered Apr 28 '16 at 12:03

Mohit Jain

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Bitwise AND with the bits from the number of characters written seems like a strange thing to do. – Thomas Padron-McCarthy Apr 28 '16 at 12:07
@ThomasPadron-McCarthy It is `fprintf(..) > 0`. `fprintf` return negative value on failure. And for float, it must return `> 0` if succesful. – Mohit Jain Apr 28 '16 at 12:09

score 1 · Answer 3 · edited May 23 '17 at 10:28

1

To see all meaningful digits in a float as text use printf("%*e", some_precision, some_float)

#include <float.h>
fprintf(f1_out, "%.*e\n", FLT_DECIMAL_DIG - 1, *vel);

edited May 23 '17 at 10:28

Community

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answered Apr 28 '16 at 12:11

chux - Reinstate Monica

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How to change output from binary to ascii?

3 Answers3