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How to Read/Write Text File and Binary File.

Posted on 2002-03-24
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Last Modified: 2013-11-15
My question is how to read/write text file and binary file one character at a time?

I try this one already.. but read nothing.  Why?

  FILE *fp;
  char temp;
  clrscr();
  if((fp=fopen("abc.txt","rt"))==NULL){
    cout<<"Error..."<<endl;
    exit(0);
  }
  else
    cout<<"No Error"<<endl;

  while(!feof(fp)){
    temp=fgetc(fp);
    cout<<"Read character="<<temp<<endl;getch();
  }


Please give me sample coding for read/write of text file and binary file.
please provide code in four methods. thanks
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Question by:yongyih
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7 Comments
 
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Accepted Solution

by:
bluprint earned 200 total points
ID: 6892380
Here are two methods, each one shows a read and a write (for a total of all 4 combinations you wanted).

****** This will open a binary file and read each character and write each character to a different file

#include<iostream.h>
#include<stdio.h>
#include<stdlib.h>


void main() {

FILE *fp, *fp2;
 char temp;
 
 if((fp=fopen("abc.txt","rb"))==NULL){
   cout<<"Error..."<<endl;
   exit(0);
 }
 else
   cout<<"No Error"<<endl;

 if((fp2=fopen("bcd.txt","wb"))==NULL){
   cout<<"Error..."<<endl;
   exit(0);
 }
 else
   cout<<"No Error"<<endl;

 temp=fgetc(fp);
 while(!feof(fp)){
      //read
   cout<<"Read character="<<temp<<endl;


   //write
   fputc(temp, fp2);

   //get next character
   temp=fgetc(fp);
 }
}

****** This will open a text file and read each character and write each character to a different file

#include<iostream.h>
#include<stdio.h>
#include<stdlib.h>


void main() {

FILE *fp, *fp2;
 char temp;
 
 if((fp=fopen("abc.txt","rt"))==NULL){
   cout<<"Error..."<<endl;
   exit(0);
 }
 else
   cout<<"No Error"<<endl;

 if((fp2=fopen("bcd.txt","wt"))==NULL){
   cout<<"Error..."<<endl;
   exit(0);
 }
 else
   cout<<"No Error"<<endl;

 temp=fgetc(fp);
 while(!feof(fp)){
      //read
   cout<<"Read character="<<temp<<endl;


   //write
   fputc(temp, fp2);

   //get next character
   temp=fgetc(fp);
 }
}
0
 
LVL 2

Author Comment

by:yongyih
ID: 6893290
thanks for reply.
but why everytime i write to a binary file, why i still can read the content of the binary file?  (still in text format)
I open the file as binary already using fopen.

tell me why, ok.  and make sure that the reading of binary file working properly or not.  

after that, i will accept your answer, thanks again.
0
 

Expert Comment

by:GEliyahu
ID: 6893731
Check out the object CFile..it's the easiest way to take care in files.
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LVL 1

Expert Comment

by:bluprint
ID: 6894233
The reason is that there is no real difference between a text file and a binary file, all files are made up of binary data.

As long as the only characters in the file are "text", that is, they have viewable values (values that a text editor knows), you will be able to read them with a text editor. If the characters have some non-viewable value, they will show up as funny looking characters.

Another difference is that some C functions will not work reading a "binary" file if it has certain types of characters, or rather, the functions won't work very predictably. When they reach the control characters, they may stop or they may keep reading. Functions like getc or putc just work one character at a time and don't care what kind of character it is.

Make sense?

Also, I ran both of these programs, and they ran fine.
0
 
LVL 1

Expert Comment

by:bluprint
ID: 6894458
After a little thought...there are a few other things about opening binary vs opening in text mode.

Opening in text mode will do some character translations.

For example, in Windows, a newline is represented by two characters, line-feed and carraige-return. When a file is opened in text mode, that two-character combination is translated into one character, represented by \n.

In binary mode, that translation doesn't occur.

There are probably lots of other examples of when character translations occur in text mode but not in binary mode...
0
 
LVL 2

Author Comment

by:yongyih
ID: 6895438
This is my problem now.. if i read from text file which has carriage return. e.g.
abc
def

in my program, it will read as abcdef or abc def
not remember has space between abc and def.

do you mind to tell me how to do the checking?
i try to check using '\n', but cannot..

anyway, i will accept your answer.

thanks for reply and hope you can reply me soon. =)
0
 
LVL 1

Expert Comment

by:bluprint
ID: 6896548
The way you check for a carraige return depends on the system you are on, and how you opened the file.

For a binary read, if a Unix/Linux system, check for \n (0A in hex), if on Windows check for (i think) \r\n (0D, 0A in hex)

That's one problem with opening something in binary, it doesn't translate the newline sequence in windows to a single character (from 0D0A to 0A).

If you open this in text mode, you can always check for \n and that's it.
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