Hi everyone I’m new to programming and this Forum. I searched the previous posts but couldn’t find an answer to my specific problem. Thanks for any help.

What I’m trying to do is read in a text file with an integer in it. I’ve read the other posts about this and could not see anything different in their programs from mine.

The file is being read as binary I used fseek and ftell to get the length of the file and I dynamically allocated a piece of memory to hold what is read using malloc. Then the file is read into memory using fread. The pointer which points to the memory block is called “cfile”.

My problem is that when I display the number read from the file I get a random number output, not the number in the file. For example when the text file has the number 7 in it, the program reads the file and for printf(“%d”, cfile[0]) outputs 2615. When I put the number 7 and a space after it in the text file, the program outputs 663607 for printf(“%d”, cfile[0]).

Here is a copy of my program:

and thanks for any help you can offer


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

int main(void)
{

FILE *fp; //file pointer
long int lfilelng; //file length


//open file
if ((fp=fopen("toberead", "rb"))==NULL) {
printf("cannot open file - 'toberead'");
exit(1);
}


if (fseek(fp, 0L, SEEK_END) !=0 ) {
printf("seek error");
exit(1);
}

lfilelng = ftell(fp);
rewind(fp);

int *cfile; /* Dynamically allocated buffer (entire file) */

if ((cfile=malloc(lfilelng+1))==NULL) {
printf("insuficient memory to read file");
exit(1);
}

if (fread(cfile, lfilelng, 1, fp) != 1) {
printf("\nread error occured");
exit(1);
}
fclose(fp);

printf("%d", cfile[0]);

free(cfile);
cfile = NULL;

return 0;
}

If you run this in a symbolic debugger or otherwise display/examine the contents of cfile after the input file is read, the problem will make itself apparent.

Why "int *" ?

Based on how the OP is printing it, i would assume the file is binary data and full of ints.

Did you see the underlined word in my post ?

Well in that case, use fscanf instead.
You are reading the integer as if it was in binary form yet you say it is in text form.

Though your suggestion quite possibly is technically correct, it masks (by the fact of its existence) the root cause of the problem IMO the OP has.

I.e. you are suggesting a fix, and I want the OP to understand the fundamental problem in his/her approach.

That answer is very Sergei Steshenkoish.
Ok i am out of this thread.

Hi, thanks for getting back so quickly to me. First, yes the file being read is a text file with an integer in it but I’m opening it as a binary file via “rb” in the line: (fp=fopen("toberead", "rb"). I did this to avoid any character translations performed on the text file so that fseek( ) would return the correct size of the file.

I used the data type of integer for the pointer “cfile” since the file contained an integer value. I thought that even though the file was being read as a binary file that the int data type was valid since the binary value read corresponded to an integer. Please correct me if I am wrong here.

I don’t understand why it was recommended to use fscanf instead of fread?

Thanks again for your help

Back to the roots. A text file is a sequence of characters, and the latter are represented in "C" by char (and not int) type. This is your fundamental problem - you have type mismatch.

1 members found this post helpful.

Use a char* instead of an int* to store the file, as the file is a string of chars, not ints.

fread treats the pointer as an array of chars, but because you read them as ints you get an int composed of 4 consecutive bytes (char's) in the file.

1 members found this post helpful.

ah ok I understand now. Thanks to everyone for your help.

So does it work now?

If so, mark the thread as Solved (in Thread Tools).

yup it works out, sorry bout the delay in marking the thread as solved wasnt sure how to do it.
thanks agian