How can I write binary to a file?

I am 71 years old and haven’t programmed in C for many years. So, this is going slow.
I am using Borland C++ IDE to write 16 bit code for a picoFlash single board computer with a 186 compatible processor and 512K of Ram. I am adding code to an existing program that takes 183 pages to print. Right now I am trying to write the contents of a string to a file opened using “wb”.
The compiler and linker don’t give any error messages.
The I have extracted the relevant code as shown below.

Code:

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#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <setjmp.h>
#include <dos.h>
#include <alloc.h>
#include <mem.h>
#include <time.h>
#include <tcp.h>
#include <conio.h>
#include "g5lib.h"
#include "cdacs.h"
#include "comms.h"
#include "comms2.h"
#include "procio.h"
 
extern char far rbuffer[4096];
                // extern because it is created by another module
                //far because I ran short of memory space
 
 
void UploadAFile(char *strDirectory,char *strFileName, int intOffset)
{
                char far *farCharPtr;
                int intNrCharsInLine;
                char strFullFileName[121];
                static FILE *TxtULFilePtr;
                int intCnt;
 
                Some code
 
                //Open file for "wb"
                TxtULFilePtr = fopen(strFullFileName, "wb");
 
                Some code to calculate farCharPtr
                Some code to calculate intNrCharsInLine
 
             
                //At this point rbuffer containes a string
                      with imbedded carriage returns and line feeds
 
                //null terminate rbuffer to avoid the need
                    to create a second large array
                rbuffer[intOffset] = '\0';                             
                //Note: If I comment out this line
                      it doesn’t change the output.
             
                //The following six lines were added
                        to verify the contents of rbuffer during test

                for(intCnt=0;intCnt<intNrCharsInLine;intCnt++)
                {
                                farCharPtr = farLinePtr + intCnt;
                                strncpy(strChar,farLinePtr + intCnt,1);
                                printf("#204D==============%s==
                                        =========\n",strChar);
                }
 
                //Write from rbuffer to file
                fprintf(TxtULFilePtr,"%s",farLinePtr);
                fclose(TxtULFilePtr);
 
}

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In a simple test case, I have a string of characters that were read from a text file. I want to write them into a new file (strFullFileName). The original file contains:

This is test line 1
This is test line 2
This is test line 3
This is test line 4

Right now the first two lines are put in a string and passed to this module in “rbuffer”.
When I run the program, the for loop gives me:

#204D==============T===========
#204D==============h===========
#204D==============i===========
#204D==============s===========
#204D============== ===========
#204D==============i===========
#204D==============s===========
#204D============== ===========
#204D==============t===========
#204D==============e===========
#204D==============s===========
#204D==============t===========
#204D============== ===========
#204D==============L===========
#204D==============i===========
#204D==============n===========
#204D==============e===========
#204D============== ===========
#204D==============1===========
#204D=========================
#204D=========================
#204D==============T===========
#204D==============h===========
#204D==============i===========
#204D==============s===========
#204D============== ===========
#204D==============i===========
#204D==============s===========
#204D============== ===========
#204D==============t===========
#204D==============e===========
#204D==============s===========
#204D==============t===========
#204D============== ===========
#204D==============L===========
#204D==============i===========
#204D==============n===========
#204D==============e===========
#204D============== ===========
#204D==============2===========
===================

When I check the new file contents, only the first line appears.

C:\>type test.txt
This is test Line 1
Question #1: How can I print the ASCII values next to the letters so I can verify that the nonprinting characters are carriage return and line feed and are not null characters?

Question #2: Is fprintf(TxtULFilePtr,"%s",farLinePtr); the correct command to put the string in the file?

Quote:

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Originally Posted by Jerry900

Question #1: How can I print the ASCII values next to the letters so I can verify that the nonprinting characters are carriage return and line feed and are not null characters?

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If you print a character with the %d format specifier, you'll get the ASCII value:

Code:

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char test = 'A';
printf("%c - %d\n", test, test);  // will print "A - 65"

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But then you need to change your debugging code:

Code:

---

for(intCnt = 0; intCnt < intNrCharsInLine; intCnt++)
{
    char c = *(farLinePtr + intCnt);  // assuming farLinePtr is a char pointer to the beginning of the string
    // alternatively: char c = farLinePtr[intCnt];
  printf("character %d: %c - %d\n", intCnt, c, c);
}

---

Quote:

---

Originally Posted by Jerry900

Question #2: Is fprintf(TxtULFilePtr,"%s",farLinePtr); the correct command to put the string in the file?

---

Yes, but why do you open the file in binary mode when you want to write text into it?

Bye, Andreas

Thank you for the input. I found a way to print ASCII. It is a little more complex than your solution.

I added the following code to my “for” loop.

Code:

---

                //Convert a string to a character to get the ASCII value
                CharChar = strChar[0];  //Convert to nondimensiond variable
                intChar = CharChar;                        //Convert to an integer
                printf("#204D==============%s===========%u\n",strChar,intChar);

---

Days ago when I first tried:

Code:

---

CharChar = strChar[0];

---

I got an error message that got me off track.

The new printout is:
#204D==============T===========84
#204D==============h===========104
#204D==============i===========105
#204D==============s===========115
#204D============== ===========32
#204D==============i===========105
#204D==============s===========115
#204D============== ===========32
#204D==============t===========116
#204D==============e===========101
#204D==============s===========115
#204D==============t===========116
#204D============== ===========32
#204D==============L===========76
#204D==============i===========105
#204D==============n===========110
#204D==============e===========101
#204D============== ===========32
#204D==============1===========49
#204D=========================0
#204D=========================0
#204D==============T===========84
#204D==============h===========104
#204D==============i===========105
#204D==============s===========115
#204D============== ===========32
#204D==============i===========105
#204D==============s===========115
#204D============== ===========32
#204D==============t===========116
#204D==============e===========101
#204D==============s===========115
#204D==============t===========116
#204D============== ===========32
#204D==============L===========76
#204D==============i===========105
#204D==============n===========110
#204D==============e===========101
#204D============== ===========32
#204D==============2===========50

This shows that I have null characters at the end of line 1. So, I need to track down where they came from.

I open the file in binary because I want to transfer binary files. The text file was just a simple test case.

Thanks again

If you truly wish to write binary then the common method is fwrite function in C
fwrite - C++ Reference