Thread: reading a file

> would you like me to post my linked list and sort alagrithem them and the work on puting the two together.
If you have a problem doing that yourself.

> the other problem that i have is that 1 i can get out of the loop.
Type EOF (ctrl+z on windows) to break the loop, just as the prompt said.

> I should be able to enter in one data and the be prompted at the list again.
> How do I do that.
Basically, turn the while loop found in amend() into an if statement. Be advised I never typed that program with the intention of you using it. Other people have made fine suggestions, such as using fgets() and sscanf() to read user input. I'm only trying to help you visualize your program so that you can appreciate the steps that need to be taken. What I posted was bare-bones, if that.

> here is what i came up for my linked list.
Linked lists with ints in them are largely for instruction purposes AFAIK. In real world programs the nodes can be much more than just that. The struct you came up with before is also a node:

Code:

typedef struct person_t {
   char FName[Nlen];
   char LName[Nlen];
   char Sex;
   char Grade;
   struct person_t *next;
} PERSON;

What you need to do is develop functions that do what you need with the node type. Like sort(), push(), pop() ... whatever you need.

> just courise how do i pass the rest of the struct so that it all prints together.
After you've built a list, pass the head node to the printing function. Have the print function walk through the list and output everything.

> So I should do the sort first then pass it to the linked list or the other way around
Build the list from your input and then sort the list, ideally.

Do not attempt to write the entire program in one sitting. Address one need at a time, and make sure that whatever you write actually works before you move on to something else.

i think this program i have been writing just kind of lost with it. i can't get it to go into the while loop. But i think i should not use a while statment there and that is causing me not to go into my loop. its nota s neat as yours but i can undertand what im doing in it.
error
92 E:\888.cpp cannot convert `FILE*' to `const char*' for argument `1' to `void perror(const char*)'
121 E:\888.cpp expected `while' at end of input
121 E:\888.cpp expected `(' at end of input
121 E:\888.cpp expected primary-expression at end of input
121 E:\888.cpp expected `;' at end of input
121 E:\888.cpp expected `}' at end of input

Code:

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


#define FLASE 0
#define TRUE 1
#define Nlen 25

typedef struct person{
     char FName [Nlen +1];
     char LName [Nlen +1];
     char Sex;
     char Grade;
     struct person *Next;
} PERSON;

void PrintList (PERSON*);
int DeletePerson;
PERSON* InsertNode (PERSON*, PERSON*);     

main ()
{
    PERSON *STU; //TEmp pointer used to creat list
    int Ans;    //User responce
    int Len, i,      //Name Length
        Deleted; //True if requested item deleted
    char FName [Nlen +1];  // first name
    char LName [Nlen +1];  // lase name
    char Grade, Sex, Ans1; 
    FILE *fin;
   
    
     
PERSON *TOP = NULL; //Initialize top list point to Null     
 fin = fopen( "e:data.txt", "rw");    
     
 do
 {
  fscanf(fin, "%25s %25s %c %c\n", STU->LName, STU->FName, &STU->Sex, &STU->Grade);   
      printf ("chose option you want to do\n");
      printf ("Option 1 : Enter New Recode\n");
      printf ("Option 2 : Display List\n");
      printf ("Option 3 : Quit\n");
       fflush(stdout);
      scanf ("%d", Ans);
       if ( scanf("%d", &Ans) == 1 ) /* get answer */
      {
         STU = (PERSON*) malloc (sizeof (PERSON));
         if (STU == NULL)
         {
            perror("PERSON");
            exit(EXIT_FAILURE);
         }
       switch(Ans){
          case '1' :       
                 printf ("\nEnter students first name ( uo to %d letters):", Nlen);
                 fgets (STU->FName, Nlen+1, stdin);
                 Len = strlen (STU->FName);
                   if (STU->FName[Len-1]== '\n')
                       STU->FName [Len-1] == '\0';
                  
                  printf ("\nEnter students first name ( uo to %d letters):", Nlen);
                 fgets (STU->LName, Nlen+1, stdin);
                 Len = strlen (STU->LName);
                   if (STU->LName[Len-1]== '\n')
                       STU->LName [Len-1] = '\0';  
                   
                 printf ("Please enter Sex");
                 scanf ("%c", &STU->Sex);
                 printf ("Please enter Grade");
                 scanf ("%c", &STU->Grade);  
                
       
       
       while (scanf("%s %s %c %c", STU->FName, STU->LName, &STU->Sex,
      &STU->Grade) == 4)
    {
     fprintf(fin, "%s %s %c %c\n", STU->FName, STU->LName, STU->Sex,STU->Grade);
     fflush(fin);
   }
   fclose(fin);
break;         

                         
             
            case '2' :
   i = 1;
   fin = fopen( "e:data.txt", "r");
    if (fin == NULL)
  {
    perror(fin);
    exit(EXIT_FAILURE);
  }
  while (fscanf(fin, "%s %s %c %c", STU->FName, STU->LName, &STU->Sex,
     &STU->Grade) == 4)
  {
    printf("Record %d: %s %s %c %c\n", i, STU->FName, STU->LName,
       STU->Sex, STU->Grade);
    i++;
  }
  fclose(fin);
        break;                 
              
              case '3' :  
                  printf ("you chose to exit.  Hit enter to close");  
                  break; 
              }//end of switch
      }  while ( Ans != 3 );
      printf("1. Enter new record\n"
             "2. Display List\n"
             "3. Quit\n\n");
      printf("Prompt: ");
      fflush(stdout);
      free(STU);
      

 getchar ();
 getchar ();
 return 0;
}

> perror(fin);
perror takes a string as an argument, not a FILE *. So you could change it to:

Code:

    perror( "e:data.txt" )

> if ( scanf("%d", &Ans) == 1 ) /* get answer */
> {
It doesn't appear you ever closed this if statement with a corresponding right brace.

ok i change it and i still ge this error message i get this every time i try to run the program help please am i getting this error because i trying to us my usb drive for two things ar once.


888.exe application error

The instrucation at "0x77c44995 referance meoary at "0x7c80b643. teh memory could not be "written'

Code:

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


#define FLASE 0
#define TRUE 1
#define Nlen 25

typedef struct person{
     char FName [Nlen +1];
     char LName [Nlen +1];
     char Sex;
     char Grade;
     struct person *Next;
} PERSON;

void PrintList (PERSON*);
int DeletePerson;
PERSON* InsertNode (PERSON*, PERSON*);     

main ()
{
    PERSON *STU; //TEmp pointer used to creat list
    int Ans;    //User responce
    int Len, i,      //Name Length
        Deleted; //True if requested item deleted
    char FName [Nlen +1];  // first name
    char LName [Nlen +1];  // lase name
    char Grade, Sex, Ans1; 
    FILE *fin;
   
    
     
PERSON *TOP = NULL; //Initialize top list point to Null     
 fin = fopen( "e:data.txt", "rw");    
     
 do
 {
  fscanf(fin, "%25s %25s %c %c\n", STU->LName, STU->FName, &STU->Sex, &STU->Grade);   
      printf ("chose option you want to do\n");
      printf ("Option 1 : Enter New Recode\n");
      printf ("Option 2 : Display List\n");
      printf ("Option 3 : Quit\n");
       fflush(stdout);
      scanf ("%d", Ans);
       if ( scanf("%d", &Ans) == 1 ) /* get answer */
         STU = (PERSON*) malloc (sizeof (PERSON));
         if (STU == NULL)
         {
            perror("PERSON");
            exit(EXIT_FAILURE);
         }
       switch(Ans){
          case '1' :       
                 printf ("\nEnter students first name ( uo to %d letters):", Nlen);
                 fgets (STU->FName, Nlen+1, stdin);
                 Len = strlen (STU->FName);
                   if (STU->FName[Len-1]== '\n')
                       STU->FName [Len-1] == '\0';
                  
                  printf ("\nEnter students first name ( uo to %d letters):", Nlen);
                 fgets (STU->LName, Nlen+1, stdin);
                 Len = strlen (STU->LName);
                   if (STU->LName[Len-1]== '\n')
                       STU->LName [Len-1] = '\0';  
                   
                 printf ("Please enter Sex");
                 scanf ("%c", &STU->Sex);
                 printf ("Please enter Grade");
                 scanf ("%c", &STU->Grade);  
                
       
       
       while (scanf("%s %s %c %c", STU->FName, STU->LName, &STU->Sex,
      &STU->Grade) == 4)
    {
     fprintf(fin, "%s %s %c %c\n", STU->FName, STU->LName, STU->Sex,STU->Grade);
     fflush(fin);
   }
   fclose(fin);
break;         

                         
             
            case '2' :
   i = 1;
   fin = fopen( "e:data.txt", "r");
    if (fin == NULL)
  {
    perror("e:data.txt");
    exit(EXIT_FAILURE);
  }
  while (fscanf(fin, "%s %s %c %c", STU->FName, STU->LName, &STU->Sex,
     &STU->Grade) == 4)
  {
    printf("Record %d: %s %s %c %c\n", i, STU->FName, STU->LName,
       STU->Sex, STU->Grade);
    i++;
  }
  fclose(fin);
        break;                 
              
              case '3' :  
                  printf ("you chose to exit.  Hit enter to close");  
                  break; 
              }//end of switch
      }  while ( Ans != 3 );
      printf("1. Enter new record\n"
             "2. Display List\n"
             "3. Quit\n\n");
      printf("Prompt: ");
      fflush(stdout);
      free(STU);

 getchar ();
 getchar ();
 return 0;
}

> scanf ("%d", Ans);
You're missing an & here:

Code:

      scanf ("%d", &Ans);

> STU = (PERSON*) malloc (sizeof (PERSON));
You don't need to cast the result of malloc. Unless you're compiling in C++ mode.

Code:

         STU = malloc (sizeof (PERSON));

> scanf ("%d", Ans);
I just noticed you already have a scanf just below this one. You can remove this one.

From my perspective, I'd say that it might be good to back up and get a handle on reading data from a file before adding more stuff. For something simple, maybe like this.

Code:

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

struct person
{
    char FName [26];
    char LName [26];
    char Sex;
    char Grade;
    struct person *Next;
};

void person_print(const struct person *student, FILE *stream)
{
    fprintf(stream, "%-25s %-25s %c %c\n",
            student->LName, student->FName, student->Sex, student->Grade);
}

int main ()
{
    static const char filename[] = "data.dat";
    FILE *file = fopen(filename, "r");
    if ( file != NULL )
    {
        struct person student;
        char line[sizeof student];
        while ( fgets(line, sizeof line, file) != NULL )
        {
            if ( sscanf(line, "%25s %25s %c %c",
                        student.LName, student.FName,
                        &student.Sex, &student.Grade) == 4 )
            {
                person_print(&student, stdout);
            }
        }
        fclose(file);
    }
    else
    {
        perror(filename);
    }
    return 0;
}

This just prints the contents of the file to the stdout (for now, later on you may want to also print to a file).

I also recommend using fgets/sscanf for the menu. With a "large enough" input buffer, this relieves you of issues of cleaning up the stdin.