Thread: reading a file

I'm trying to do Write a C program that displays a three option menu of: 1. Enter A Record, 2. Display List, 3. Terminate. Option 1 should ask for Last Name (character string up to 25 long), First Name (character string up to 25 long), Sex (enumerated data type of M/F), Grade (enumerated data type of A/B/C/D/F). The data should be placed in a structure and inserted into a linked list ordered by Last Name. Option 2 should list all records on the screen. Option 3 should write the linked list to a disk file and exit. When the program is invoked it should read the existing data in the disk file if it exists before displaying the menu. After options 1 and 2 are complete the menu should be displayed again.

I'm having an issues etting up the file to be read. ANd ideas this is what i have gotten so far.

Code:

 #include <stdio.h>
#include <string.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
    char ANS;    //User responce
    int Len,      //Name Length
        Deleted; //True if requested item deleted
    char FName [Nlen +1];  // first name
    char LName [Nlen +1];  // lase name
    char Grade, Sex; 
    FILE *fin;
     fin = fopen( "data.dat", "rw");
     
PERSON *TOP = NULL; //Initialize top list point to Null     
    
     
 while (fscan(fin, %-*s %-*s %c %c\n, Nlen, STU->LName, STU->FName, STU->Sex,STU->Grade) != EOF){
      
 
 getchar ();
 getchar ();
 return 0;
}

I need to store it as text.

Code:

while (fscan(fin, '%-*s %-*s %c %c\n", Nlen, STU->LName, STU->FName,
STU->Sex,STU->Grade) != EOF)

dose this look right for know

Code:

  #include <stdio.h>
#include <string.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,      //Name Length
        Deleted; //True if requested item deleted
    char FName [Nlen +1];  // first name
    char LName [Nlen +1];  // lase name
    char Grade, Sex; 
    FILE *fin;
     fin = fopen( "data.dat", "rw");
     
PERSON *TOP = NULL; //Initialize top list point to Null     
    
     
 while (fscanf(fin, "%-*s %-*s %c %c\n", Nlen, STU->LName, STU->FName, STU->Sex,STU->Grade) != EOF){
      printf ("chose option you want to do\n");
      printf ("Option 1 : Enter New Recode");
      printf ("Option 2 : Display List");
      scanf ("%d", Ans);
      
       switch (Ans){
          case '1' :       
             do {
              STU = (PERSON*) malloc (sizeof(PERSON));
              if (STU == NULL)
                printf ("Error -- could not allocate memory\n\n");
              else {
                 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);  
                 STU->Next= NULL;          
               
 
 getchar ();
 getchar ();
 return 0;
}

so what your saying is that i do not need -* in there just teh s to say that it is a string

but know im getting this error message 44 H:\My Documents\Untitled1.cpp `malloc' undeclared (first use this function) on thsi line what dose it mean.

Code:

STU = (PERSON*) malloc (sizeof(PERSON));

Originally Posted by redmondtab

but know im getting this error message 44 H:\My Documents\Untitled1.cpp `malloc' undeclared (first use this function) on thsi line what dose it mean.

If I'm not mistaken, the compiler cannot locate the prototype for malloc, so you must add this somewhere in your code:

Code:

#include <stdlib.h>

The fprintf() function prints to a file.

i want to print whats in the file to the screen. Did i not read it in.

Originally Posted by redmondtab

i want to print whats in the file to the screen. Did i not read it in.

Actually no you did not, if answer is ever equal to two before it equals one. The switch-case would jump to that case and try to print a bunch of presumably empty values. Please check your logic.

And it won't even appear on the screen since you called printf incorrectly, winning you a compile-time error.

so if i write it like this will it pull it from the file and print the data to the screen, becuase that is what i want to do. IF there is data in the file priint the list. IF there is no data. Then as the user to input the data. or is there a bette way to write that statment. BEcasue i know i still need to put it into a loop with an option to teremat. But i wanted to do it in small steps so that i could walk though what i was doing and get the code correct as i went.

Code:

printf (fin, "%s %s %c %c\n",  LName, FName, Sex,Grade);

I hope no one minds this, but I've been making some attempts. Maybe something like this is closer to what the OP wants:

Code:

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

#define Nlen    26

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

void amend_file( char file[], PERSON *STU );
void show_file( char file[], PERSON *STU );

int main ( void )
{
   PERSON *STU;
   int Ans;
   char file[] = "data.txt";

   do
   {
      printf("1. Enter new record\n"
             "2. Display List\n"
             "3. Quit\n\n");
      printf("Prompt: ");
      fflush(stdout);
      if ( scanf("%d", &Ans) == 1 ) /* get answer */
      {
         STU = malloc(sizeof *STU);
         if (STU == NULL)
         {
            perror("PERSON");
            exit(EXIT_FAILURE);
         }
         switch(Ans)
         {
            case 1:
               amend_file(file, STU);
               break;
            case 2:
               show_file(file, STU);
               break;
            case 3: default:
               Ans = 3;
               break;
         }
      } /* /get answer */
   }
   while ( Ans != 3 );
   free(STU);
   return EXIT_SUCCESS;
}
/*
 * amend_file: Enter stuff into the working file.
 * Very much a bare bones function so far; work on making this better
 * Perhaps make it work with a linked list, as your struct suggests?
 */
void amend_file( char file[], PERSON *HEAD )
{
   assert(HEAD != NULL);
   FILE *fin = fopen(file, "a");
   if ( fin == NULL )
   {
      perror(file);
      exit(EXIT_FAILURE);
   }
   printf("Enter new record (EOF to quit): ");
   while (
    scanf("%s %s %c %c", HEAD->FName, HEAD->LName, &HEAD->Sex,
      &HEAD->Grade) == 4
   )
   {
     fprintf(fin, "%s %s %c %c\n", HEAD->FName, HEAD->LName, HEAD->Sex,
        HEAD->Grade);
     fflush(fin);
   }
   fclose(fin);
}
/*
 * show_file: Reads the working file.
 * Bare bones again...
 */
void show_file ( char file[], PERSON *HEAD )
{
  assert(HEAD != NULL);
  int i = 1;
  FILE *fout = fopen(file, "r");
  if (file == NULL)
  {
    perror(file);
    exit(EXIT_FAILURE);
  }
  while (
   fscanf(fout, "%s %s %c %c", HEAD->FName, HEAD->LName, &HEAD->Sex,
     &HEAD->Grade) == 4
  )
  {
    printf("Record %d: %s %s %c %c\n", i, HEAD->FName, HEAD->LName,
       HEAD->Sex, HEAD->Grade);
    i++;
  }
  fclose(fout);
}

I was able to make this text file.
$ ./a
1. Enter new record
2. Display List
3. Quit

Prompt: 1
Enter new record (EOF to quit): Tom Capobres M B
George Carlin M A
Frank Sinatra M C
Matt Outlaw M A
Betsy Storrs F B
1. Enter new record
2. Display List
3. Quit

Prompt: 2
Record 1: Tom Capobres M B
Record 2: George Carlin M A
Record 3: Frank Sinatra M C
Record 4: Matt Outlaw M A
Record 5: Betsy Storrs F B
1. Enter new record
2. Display List
3. Quit

Prompt: 3

Sorry it's just so ugly though...

> BEcasue i know i still need to put it into a loop with an option to teremat
As you read parts of the file I would believe that is a loop with a requirement to terminate eventually.

>IF there is data in the file priint the list. IF there is no data. Then as the user to input the data.
-Read data from the file first.
-If that fails, ask the user if there is more data
-If yes, get input from the user and store it somewhere. If no, exit.
-Print that to the file using something like fprintf()
-loop

Code:

scanf("%d", &Ans);

The first argument to printf is and always was a format string, not a FILE *

Code:

printf ("%s %s %c %c\n",  LName, FName, Sex,Grade);