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
– user694733, Commented Apr 28, 2016 at 12:05

Thomas Padron-McCarthy · Accepted Answer · 2016-04-28 12:03:08Z

2

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]);
}

answered Apr 28, 2016 at 12:03

Thomas Padron-McCarthy

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Mohit Jain · Accepted Answer · 2016-04-28 12:03:11Z

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, 2016 at 12:03

Mohit Jain

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2 Comments

Thomas Padron-McCarthy Over a year ago

Bitwise AND with the bits from the number of characters written seems like a strange thing to do.

Mohit Jain Over a year ago

@ThomasPadron-McCarthy It is fprintf(..) > 0. fprintf return negative value on failure. And for float, it must return > 0 if succesful.

Community · Accepted Answer · 2017-05-23 10:28:11Z

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, 2017 at 10:28

CommunityBot

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answered Apr 28, 2016 at 12:11

chux

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