problem reading files in C

I'm using the fgetc() function for reading files.Aside from reading files I want it to read files such as EXEs as well.I test it by using a hex editor to insert 0200 0242 and then run the program.The problem is when I put it after a hex string like 0000 0000 0000 0000 the program will not read it instead it will terminate.Otherwise it will read it and report the match

Code:

---

int dvd_chk(FILE *x)
{
int num_chk=0;
char c;
while( (c = fgetc( x )) != EOF )
{
if ( c == 0x02 ) { c=fgetc(x);
if ( c == 0x00 ) { c=fgetc(x);
if ( c == 0x04 ) { c=fgetc(x);
if ( c == 0x24 ) { num_chk++; }
}}}
}
fclose( x );
return match;

---

hmmm....I'm not so sure if you can do that, read in a char and test it with a hex value. probably can...I'm not too sure about it, though.

Also, you need to open the file - try adding....

x = fopen("somefile.txt","rb"); //you need to open it as rb which is reading in binary mode

to your first line of code in that function.

I open the file through main and pass the file pointer to the function.I've tested it by using Hex Workshop and adding the hex string 0200 0424.I tried it on a text file and an EXE.Here is the full code:

Code:

---

#include <stdio.h>

int dvd_chk(FILE *x);

int main(int argc, char *argv[])
{
FILE *inf;
int noc;
printf("DVD Check finder\n\n");
if (argc!=2){
printf("insufficient program usage\n");
printf("usage: dvdchk <file to be scanned>\n");
return 0;
}
inf=fopen( argv[1], "rb" );
if (inf==null){
printf("File %s does not exist\n");
return 0;
}
noc=dvd_chk(inf);
printf("Number of Checks: %d\n",noc);
return 0;
}

int dvd_chk(FILE *x)
{
int match=0;
char c;
while( (c = fgetc( x )) != EOF )
{
if ( c == 0x02 ) { c=fgetc(x);
if ( c == 0x00 ) { c=fgetc(x);
if ( c == 0x04 ) { c=fgetc(x);
if ( c == 0x24 ) { match++; }
}}}
}
fclose( x );
return match;
}

---

HHHHHHMMMM

don't you need to use fread() to read binary files?

Quote:

---

Originally posted by SPOOK
HHHHHHMMMM

don't you need to use fread() to read binary files?

---

I think fgetc should work fine if the file is opened in the binary mode.

from http://www.acm.uiuc.edu/webmonkeys/book/c_guide
*************************************************
Declaration:

int fgetc(FILE *stream);
Gets the next character (an unsigned char) from the specified stream and advances the position indicator for the stream.
On success the character is returned. If the end-of-file is encountered, then EOF is returned and the end-of-file indicator is set. If an error occurs then the error indicator for the stream is set and EOF is returned.
*************************************************

Doesnt put any restrictions on the stream . As far I know , in most unix C compilers there is no difference between the modes , in windoze/dos I think the \r\n combination is converted to a single \n while reading and \n is output as \r\n while writing in the text mode , I may be wrong .

Your problem (I believe) is with the way you're checking EOF. EOF is not in the range of a char. You should use an integer for 'c'. All 'is*()' functions, '*getc()' functions, *putc() functions, take and receive a "char" as an "int". EOF is _NOT_ in the range of a char.

Code:

---

int dvd_chk(FILE *x)
{
  int match=0;
  int c;

  if( x == NULL ) return -1;

  while( (c = fgetc( x ) ) != EOF )
  {
      if ( c == 0x02 ) { c=fgetc(x);
        if ( c == 0x00 ) { c=fgetc(x);
            if ( c == 0x04 ) { c=fgetc(x);
              if ( c == 0x24 ) { match++; }
      }}}
  }
  fclose( x );
  return match;
}

---

Why are you closing the file in this function? You don't open it here, why close it here?

Quzah.

Quote:

---

Originally posted by SPOOK
HHHHHHMMMM

don't you need to use fread() to read binary files?

---

yes

I think you can use feof() to judge the end of the file , You can have a test.
It's my suggestion.

Quote:

---

Originally posted by swoopy


yes

---

Why do you think only fread and fwrite can be used with binary files and not fgetc ? I havent seen any such thing in any reference .
This code copied all whatever exes in windoze I tried perfectly.

#include <stdio.h>
int main(void)
{
int c;
FILE *fin,*fout;
char bufin[256],bufout[256];
printf("Give the name of the input file:");
gets(bufin);
printf("Give the name of the output file:");
gets(bufout);
fin=fopen(bufin,"rb");
if(fin==NULL)
{
printf("Unable to open %s\n",bufin);
perror(NULL);
return 1;
}
fout=fopen(bufout,"wb+");
if(fout==NULL)
{
printf("Unable to create %s\n",bufout);
perror(NULL);
return 1;
}
while( (c=fgetc(fin)) != EOF) fputc(c,fout);
return 0;
}

pinko_liberal,

yes, you are right. My mistake.