Problem using fwrite and fread with files.

Question

0.00/5 (No votes)

See more:

So this the code which is giving me problem in Visual C++ 2010 Express. I don't have this problem if a compile it and execute it with gcc in Ubuntu:

FILE * pFile;
char buffer[] = { 'x' , 'y' , 'z' };

pFile = fopen ( "myfile.bin" , "wb" );
fwrite (buffer , 1 , sizeof(buffer) , pFile );
fread(buffer,1,sizeof(buffer),pFile);

printf("%c,%c,%c",buffer[0],buffer[1],buffer[2]);

The problem is that whenever I try to write into the file with the fwrite function it writes me garbage characters.
Because when I try to retrieve them with fread and I print them with printf,contents of the buffer have changed to '='.

Even if I put the file mode to "w" and I open the file with the notepad I see it correctly but there are garbage characters at the end of the file.
So I don't know why this is happening.
The thing is that I have copied this exact example from here and it should be working fine.

http://www.cplusplus.com/reference/cstdio/fwrite/[^]

Posted 5-May-13 11:21am

unscathed18

Add a Solution

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

CPallini · Accepted Answer · 2013-05-05T11:59:00

You program is incorrect. In order to read the written data, you have to (re)position the 'file pointer' at the very beginning of the file. This can simply accomplished by closing the file and then open it again for reading.

C

//...
pFile = fopen ( "myfile.bin" , "wb" );
fwrite (buffer , 1 , sizeof(buffer) , pFile );
fclose(pFile);
fopen ( "myfile.bin" , "rb" );
fread(buffer,1,sizeof(buffer),pFile);
//...

By the way: you should always check the return value of the called functions.