Re: Problem with fread

Re: Problem with fread

[Eljay Love-Jensen]

Hi Ajay,

fread does not append a '\0' (null character) at the end of a buffer.

Regarding your test_fread.cpp attachment...

You shouldn't use #include <string.h>, you should use #include <cstring>.

You shouldn't use #include <stdlib.h>, you should use #include <cstdlib>.

You shouldn't use #include <errno.h>, you should use #include <cerrno>.

I strongly urge you to consider using string objects and the #include 
<string> header, instead of fixed character buffers.

I strongly urge you to use fstreams and #include <fstream>, instead of 
FILE, fopen, stat, et al.

I strongly urge you to use C++ new/delete instead of C 
malloc/calloc/realloc/free.

I'll send you my refactoring of your test_fread.cpp shortly.  (Not to the 
forum.)

Sincerely,
--Eljay

Problem with fread

[Ajay Bansal]

[-- Attachment #1.1: Type: text/plain, Size: 438 bytes --]

Hi All
 
We are using fread to read the entire contents of the file in a buffer.

Does fread append "\0" at the end of the buffer or we have to do it
manually?
 
Attached is a sample program. We are using the test function twice.
Second time when we call the fucntion, give file has a smaller size then
what was given at the first call. 
 
Second time, output is gargled towards end.
 
any idea???
 
Regds
Ajay Bansal
 

[-- Attachment #1.2: Type: text/html, Size: 1572 bytes --]

[-- Attachment #2: test_fread.cpp --]
[-- Type: application/octet-stream, Size: 1884 bytes --]

#include        <iostream>
#include        <string.h>
#include        <stdlib.h>
#include        <errno.h>
#include        <sys/stat.h>

using namespace std;

void test(char *, char*);

int main()
{
        char filename[20];
        char *buffer;

        cout<<"Please enter the file name : ";
        cin>>filename;

        test(filename, buffer);
        cout<<"Please enter the file name : ";
        cin>>filename;
        test(filename, buffer);

}



void test(char *filename, char *buffer)
{
        FILE *fd=NULL;
        int nbytes;
        struct  stat    s;
        int filesize=0;

        buffer=NULL;

        fd = fopen(filename, "ro");

        if(fd == NULL)
        {
                cout<<"We have some error"<<endl;
                return;
        }

        if(stat(filename, &s) == -1)
        {
                cout<<"We have some error"<<endl;
				return;
        }

        nbytes = s.st_size;
        cout<<"1. File size is : "<<nbytes<<endl;

        buffer = (char*) malloc(nbytes, 0);

        fread(buffer, nbytes, 1, fd);

        if(ferror(fd))
        {
                fclose(fd);
                cout<<"We have some error"<<endl;
                return;
        }



        for(int i=0;i<nbytes+1;i++)
        {
                if (buffer[i] == '\0')
                {
                        cout<<"xxxxx"<<endl;
                        cout<<buffer[i]<<endl;
                        cout<<"We found the \0"<<endl;
                        break;
                }
                else
                        filesize++;
        }

        cout<<"2. File size is : "<<filesize<<endl;
        cout<<"Buffer is : "<<"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"<<endl<<buffer<<endl<<"********************"<<endl;

        free(buffer);

        return;

}