Re: fread can not read particular data

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• In reply to: Meenakshi Matai: "fread can not read particular data"
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Date: 24 Jun 2004 12:58:32 GMT

On Wed, 23 Jun 2004, Meenakshi Matai wrote:

> I am trying to read data from a .dat file using fread.
>
> This is how my syntax looks:
> temp = fread(indata, sizeof(short int), 1, datafile);

Insufficient information. Whenever you post a code snippet, give the data
types and how they were initialized. This posting is missing the
following:

1) what is the data type of indata?
2) how was indata initialized?
3) what is the data type of datafile?
4) how was datafile initialized?

I can only guess that this is what you have:

#include <stdlib.h>

        short int *indata; /* answers #1 */
        FILE *datafile; /* answers #3 */

        indata = malloc(sizeof(short int)); /* answers #2 */
        if(indata == NULL) exit(EXIT_FAILURE);

        datafile = fopen("filename.dat", "r"); /* answers #4 */
        if(datafile == NULL) exit(EXIT_FAILURE);

        fread(indata, sizeof(short int), 1, datafile);

> I looked into the data file in Hex format and saw that everytime fread
> finds the data "1A" it returns a non-zero value.
>
> I tried with another .dat file and the same thing happens.
> I went in and manually changed the contents of the .dat file.
> Everywhere I found a "1A" I changed it to "1B" ("1C", "1D", "0D") and
> it works just fine.
> Anything but "1A" works fine.
>
> Could you please suggest why this would be happening.

The binary value 0x1A just happens to be the ASCII value CTRL-Z. On
MSDOS/Windows systems, CTRL-Z is the EOF for text files.

Problem: you have opened a binary file in text mode.
Solution: open the binary file in binary mode.

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• Previous message: Emmanuel Delahaye: "Re: Callbacks in C"
• In reply to: Meenakshi Matai: "fread can not read particular data"
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