Question

I’ve never had so much trouble writing data to files! I’m running GCC from MinGW, because I’m used to using GCC in Linux. I usually use the Linux system calls open(), write(), and read(), but I’m writing a Windows program now and I had trouble using read()/write() in Windows, so I’m just using the standard libraries. Anyway, the problem I’m having is I have no idea how to write to a file! I’ve defined “FILE *” variables, used fopen(), with “r+b”, “wb”, and “w+b”, but I still cannot write to my output file with fwrite() or fprintf(). I don’t know what I’m even doing wrong! Here’s my source:

#include <limits.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <strings.h>

#define DEBUG   1

/*** Global functions ***/
double  highfreq(double deg);

/*** Global variables ***/
double  sin_now;

unsigned int    *ptr;
unsigned char   *key,   *infilename,    *outfilename;
FILE    *infile,    *outfile,   *keyfile;

const char  *pipe_name="[pipe]";

int main(int argc, char *argv[]) {
    unsigned int    x,  y,  z;

    if(argc!=3) {
        fprintf(stderr, "Syntax error: %s <infile.txt> <outfile.wav>", argv[0]);
        return 1;
    }
    if(argv[1][0]=='-') {
        infile=stdin;
        infilename=(unsigned char *)pipe_name;
    }
    else {
        infilename=argv[1];
        if((infile=fopen(infilename, "rb"))==NULL) {
            fprintf(stderr, "Could not open input file for modulation.\n", infile);
            return 2;
        }
    }
    if(argv[2][0]=='-') {
        outfile=stdout;
        outfilename=(unsigned char *)pipe_name;
    }
    else {
        outfilename=argv[2];
        if((infile=fopen(outfilename, "wb"))==NULL) {
            fprintf(stderr, "Could not open/create output file for modulation.\n", outfile);
            return 3;
        }
    }
    if(DEBUG) printf("Input file:\t%s\nOutput file:\t%s\n", infilename, outfilename);

    fprintf(outfile, "Why won't this work!?\n");

    fclose(infile);
    fclose(outfile);
    return 0;
}

double highfreq(double deg) {
    double  conv,   rad;

    conv=M_PI/180;
    rad=deg*conv;
    return sin(rad);
}

I’m eventually going to make a WAV file as output, hence the “highfreq()” function, but for now I can’t even get it to write to a file! fprintf() returns with an error value of -1, if that helps anyone. I don’t really understand, though because from what I read, this simply indicates there was an error, but nothing more.

Answer 1

    outfilename=argv[2];
    if((infile=fopen(outfilename, "wb"))==NULL) {

That’s the second time in your code you assign the result of fopen to infile. You probably wanted outfile there.