Thread: reading from files

sorry for reviving this thread but ive been working so havnt had much of a chance to continue with my learning of c. when i try and open the file it doesnt seem to be finding it, where should the file be placed? here is my code, there may be something wrong:


list.h

Code:

  

/*List header file */

#include <stdio.h> /* Header file includes the file stdio.h 
                    because that is where NULL is defined*/
                    
typedef char DATA[30];  /* Creates names of types that are more 
                    suggestive of their use*/

typedef struct linked_list {
    DATA d;
    struct linked_list *next;
} Element;

typedef Element* LINK;

time_lib.h

Code:

 

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

#define MAXSTRING 100

typedef struct {
        clock_t   begin_clock,  save_clock;
        time_t    begin_time,   save_time;
} time_keeper;

static time_keeper  tk;  /* tk is external to the functions and is used
                         for communication between the functions in this
                         file */

void start_time(void)   /* when start_time() is invoked, the values returned
                           from clock() and time() are stored in tk */
{
     tk.begin_clock = tk.save_clock =clock();
     tk.begin_time = tk.save_time = time(NULL);
}

double prn_time(void) /* When prn_time() is invoked, new values from clock()
                      and time() are used to compute and print the elapsed user
                      time and the elapsed real time, and new values are stored
                      in tk*/
{
       char s1[MAXSTRING], s2[MAXSTRING];
       int field_width, n1,n2;
       double clocks_per_sec = (double) CLOCKS_PER_SEC,
              user_time, real_time;
              
user_time = (clock() -tk.save_clock) / clocks_per_sec;
real_time = difftime(time(NULL),tk.save_time);
tk.save_clock =clock();
tk.save_time =time(NULL);

sprintf(s1, "%.1f", user_time);
n1 = strlen(s1);
sprintf(s2, "%.1f", real_time);
n2 =strlen(s2);
field_width = (n1>n2)? n1 :n2;
printf("%s%*.1f%s\n%s%*.1f%s\n\n",
   "User time: ", field_width, user_time, "seconds",
   "Real time: ", field_width, real_time, "seconds");
   return user_time;
}

list.c

Code:

#include "list.h"
#include "time_lib.h"
#include <stdlib.h>
#include <string.h>


/*Function to create a list recursivly*/

LINK create( DATA h, Element *t )
{
    LINK y = calloc( 1, sizeof( Element ) );
    strcpy( y->d, h );
    if ( t ) t->next = y; /* Only do this if there is a previous element. */
    return y;
}

/* Function to read data from file*/

FILE *readdata(void)
{
  FILE *ifp;    /*infile pointer*/
  ifp=fopen("birthday.txt","r");   /*Open file birthday for reading only*/
  if(ifp==NULL)
  {
      printf("File Cannot Be Opened\n");
  }
  return ifp;

}

/* Function to insert data into the list*/    

LINK insert(FILE *ifp)
{
    LINK head = NULL;
    LINK tail = NULL;
    DATA b;
    while( fscanf( ifp, "%s", b ) == 1 ){
           tail = create( b, tail );
           if( !head ) { head = tail; }
    }
    printf("\n");
   return head;  
} 

/* Function to count the number of elements in the list recursively */

int count(LINK head)
{
    if(head==NULL) /* If the list is empty , 0 is returned , otherwise
                      the number of elements in the list is returned */
         return 0;
    else           
         return (1+count(head->next));
} 

/*Function to print list*/

void print_list(LINK head)
{
    /* This 'for' loop executes while head !=0 */
    LINK next;
    for( ; head ; head = next ) {
    printf( "%s\n", head->d );
    next = head->next;
    }
}    
         
        
int main(void)
{
    LINK head = NULL;
    FILE *ifp;
    start_time(); /* function call to start time in time_lib.h */
    readdata();
    head=insert(stdin);
    prn_time(); /* function call to print time in time_lib.h */
    count(head);
    print_list(head);
    fclose(ifp);
    return 0;
}

Originally Posted by recluse

thanks sean , its now opening the file but not doing anything else, is it in another endless loop somewhere?

i get 1 compiler warning : local variable 'ifp' used without having been intialized. is this causing my program not to work?

Code:

FILE *ifp;
start_time(); /* function call to start time in time_lib.h */
readdata();
...
fclose(ifp);

See the problem?

Quzah.

>no sorry quzah , i dont see the problem
You're trying to fclose a file pointer that was never initialized.

Why not just delete it since it's not being used?

Code:

FILE *readdata(void)
{
  FILE *ifp;    /*infile pointer*/
  ifp=fopen("birthday.txt","r");   /*Open file birthday for reading only*/
  if(ifp==NULL)
  {
      printf("File Cannot Be Opened\n");
  }
  return ifp;

}

Combine with the previously mentioned:

Code:

FILE *ifp;
start_time(); /* function call to start time in time_lib.h */
readdata();
...
fclose(ifp);

How about now? Now do you see the problem? Here's a hint: What happens to the return value of readdata?

Quzah.

sorry i'm still confused can i not just do what prelude said and remove FILE *ifp from main , as it has been declared in my readdata function?

You're not inserting correctly:

Code:

LINK insert(FILE *ifp)
{
    LINK head = NULL;
    LINK tail = NULL;
    DATA b;
    while( fscanf( ifp, "%s", b ) == 1 ){
           tail = create( b, tail );
           if( !head ) { head = tail; }
    }
    printf("\n");
   return head;  
}

What happens if head is not null? What do you do with tail? (Hint: Nothing at all!)

[edit]
No, I correct myself: The problem is in the function create. You aren't linking nodes correctly:

Code:

LINK create( DATA h, Element *t )
{
    LINK y = calloc( 1, sizeof( Element ) );
    strcpy( y->d, h );
    if ( t ) t->next = y; /* Only do this if there is a previous element. */
    return y;
}

What you should be doing is making y->next equal t. Not the other way around.
[/edit]

Quzah.