Thread: problem with reading from a file

heres the problem trying to read in a text file(sample below) and read these values into an array, i will use the array to check for valid users.

n123456
origam3
k987654
n290865

heres the code

Code:

#include <stdio.h>

main()
{
  FILE *stream;
  stream = fopen("passwords1", "r");
  
  if (stream == NULL)
  {
    printf("File Not Loaded Correctly");
  }
  char linebuffer[10];
  char *users[2];
  int i =0;
    
  while(fgets(linebuffer, 10, stream))
  {
    sscanf(linebuffer,"%s", &users[i]);
    printf("%s\n", &users[i]);
    i++;
  }
    
  printf("\n");
  
  for(i=0;i != 4;i++)
  {
    printf("Value:%s\n",&users[i]);
  }
}

//output produced by first printf with the while loop
n123456
origam3
k987654
n290n29

//output produced from second printf outside of the stream
Value:n123orign290n290n29
Value:orign290n290n29
Value:n290n290n29
Value:n290n29

as u can see the code prints out correctly when accesing the first printf except fot the last one, but not when im accessing the one outside of the loop, this has been doing my head in for ages, any help much apreciated, cheers

a1dutch

Code:

  while(fgets(linebuffer, 10, stream))
  {
    sscanf(linebuffer,"%s", users[i]);
    printf("%s\n", users[i]);
    i++;
  }

Try this code. I think you're reassigning to a pointer over and over again.

You see, users[i] evaluates to *(users+i), so you needn't give sscanf or printf a reference to it. In other words, arrays are always passed by reference because they're basically pointers.

i havent allocated any memory to

Code:

 users[2]

whats the easiest way to do this?

without the & it wont print out!

sorry if im a bit dumb, i learnt java and now moving to C, its a lot harder when dealing with strings!

joshdick i chnaged it to, it dosent even comppile now!

Code:

 
  while(fgets(linebuffer, 10, stream))
  {
    sscanf(linebuffer,"%s", users[i]);
    printf("%s\n", users[i]);
    i++;
  }

and it comes up with a compile error

Code:

clients.c:33: error: syntax error before "origam3"
make: *** [clients] Error 1

Originally Posted by a1dutch

clients.c:33: error: syntax error before "origam3"

It looks like your error is before "origam3." Look around there for your syntax error.

dave i use sscanf as the original text file is user then whitespace(of no fixed length) then password

n290865 password
n456832 passwords
n297236 password

mate ur a legend, cheers. does sscanf require u to check the result is ok?

e.g as in the code

Code:

if ( sscanf(line, "%9s", user[i]) == 1 )

cos if i take it out of the if statement it dosent work?

cheers for ur help

mate i tried changing that code u posted to read the password into another array,but it just aint having it, heres what ive put

Code:

#include <stdio.h>
#include <string.h>

int main(void)
{
   FILE *file = fopen("passwords", "r");
   if ( file != NULL )
   {
      char line[80];
      char user[5][10];
      char userpw[5][10];
      
      size_t count, i = 0;
      while ( fgets(line, sizeof line, file) != NULL )
      {
         if ( sscanf(line, "%9s %s", user[i], userpw[i]) == 1 )
         {
            if ( ++i >= sizeof user / sizeof *user )
            {
               break;
            }
         }
      }
      fclose(file);
      for ( count = i, i = 0; i < count; ++i )
      {
         printf("user[%d] = \"%s\",Password:%s\n", (int)i, user[i], userpw[i]);
      }
   }
   return 0;
}

also im gunna buy a C book do you recomend any??

cheers

There are countless threads in this board asking for book recommendations. The only C/C++ book I keep on my desk at work, though, is the C/C++ Programming Reference by Schildt. It's a very handy thing to keep around while programming. However, that's a reference book, not a teaching one, so search the board for those kinds of books.

I haven't run into any of the errors that others have pointed out, and I think he's a rather good writer. That book has always had the information I wanted.

What C++ reference book do you use, praytell? And please don't tell me The C++ Programming Language...