在 C 文件中读取二进制文件的第一个字符时出现问题

Question

I am trying to read a binary file and its content.

/*aoObj.fb is the pointer of the file (e.x. FILE *fp)*/

char ch;
aoObj.fp = fopen(aoObj.f_name, "rb");

if (aoObj.fp == NULL)

      {
        perror("Error while opening the file.\n");
        exit(EXIT_FAILURE);
      }

        /* /\*list all strings *\/ */
        printf("\n\nThe content of the file: \n");

        while ((ch = fgetc(aoObj.fp)) != EOF)
          printf("%c", ch);

        fclose(aoObj.fp);
        (void) opt_free(&aoObj);
        return 0;
}

But I am facing issues when I print the content of thi file because only the first character of the input isn't printed ok, as follows:

May I know why this is happening?

EDIT: All the variables which are being read are declared as STRINGS

Answer 1

The OP states the file contents are 'binary' not 'text' Therefore, accessing the file should be via the I/O operators made for binary files,

Suggest:

size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream);

Since the data read from the 'binary' file is NOT ascii characters, it is an 'error' to try to print those 'binary' characters with the 'output format conversion' specifier: %c .

Suggest:

printf( "%02x\n", ch );

Note: the %02x so a leading nibble of 0x0 will be printed rather than suppressed.

When the code is corrected to use: fread() rather than fgetc() the declaration of ch can/should be unsigned char ch; so no need to change that to int ch;

The following proposed code:

1. cleanly compiles
2. performs the desired functionality
3. is missing a main() function and the passing of the parameter: f_name so does not link
4. properly checks for an error when opening the input file
5. uses the returned value from fread() to 'assume' EOF, however, it may be instructive (and for robust code) to check the value of errno just to assure there was no other error.
6. documents why each header file is included

Note: the proposed code is not very efficient as it only reads a single byte at a time rather than a whole buffer full of bytes

Note: the proposed code will output one byte contents (in hex) on a single line. You might want to modify that to output several bytes contents (in hex) before moving to a new line.

and now, the proposed code:

#include <stdio.h>    // FILE, fopen(), perror(), printf(), fclose()
                      // fread()
#include <stdlib.h>   // exit(), EXIT_FAILURE

void myfunc( char *f_name )
{
    unsigned char ch;
    FILE *fp = fopen( f_name, "rb");
    if (fp == NULL)
    {
        perror("Error while opening the file.\n");
        exit(EXIT_FAILURE);
    }

    /* /\*list all strings *\/ */
    printf("\n\nThe content of the file: \n");

    size_t bytesRead;
    while ( ( bytesRead = fread( &ch, 1, 1, fp ) ) == 1 )
    {
        printf("%02x\n", ch);
    }

    fclose(fp);
}

Answer 2

You declared ch as char but you should have declared it as int .