fseek()

Question

donelliewhyte -7 Newbie Poster

14 Years Ago

Thanks for your help so far that i have achieved my goal.

My other problem is updating a particular record using fseek()

void updaterecord(void)
{
     
   system("color 2");
   
   struct custinfo info;
   
   FILE *customer1;   
    
   
   customer1=fopen("customer1.txt","r");
   
   if (customer1==NULL)
            printf("\n\n\t\t\t  FILE WAS NOT FOUND ");
    else
         {
              char choice4; 
              char Target[50];
              int Found=0;
              
              
              if((customer1=fopen("customer1.txt","r"))==NULL)
                   printf("THE FILE IS EMPTY");
              else
              {
                  printf("\n\n\t\t ENTER ID NUM:");
                  scanf("%s",&Target);
                  while(!feof(customer1)&& Found==0)
                      {
                                    
                        fscanf(customer1,"%s %s %s %s %s %s %s %s",info.regis,info.Name,info.address,info.number,info.dob,info.treatment,info.allergies,info.app);
               
                        if(strcmp(Target,info.regis)==0)
                        Found=1;
                      }
                     
                      if(Found)
                      {                                              
                           
                        printf("\n\t\t  REGISTRATION:%s\n",info.regis);
                        printf("\n\t\t  NAME:%s\n",info.Name);
                        printf("\n\t\t  ADDRESS:%s\n",info.address);
                        printf("\n\t\t  NUMBER:%s\n",info.number);                       
                        printf("\n\t\t  DATE OF BIRTH:%s\n",info.dob); 
                        printf("\n\t\t  LAST TREATMENT:%s\n",info.treatment); 
                        printf("\n\t\t  ALLERGIES:%s\n",info.allergies);    
                        printf("\n\t\t  LAST APPOINTMENT:%s\n",info.app); 
                        
                        rewind(customer1);

                        fseek(customer1,sizeof(info),SEEK_SET);

                        fscanf(customer1,"%s %s %s %s %s %s %s %s",info.regis,info.Name,info.address,info.number,info.dob,info.treatment,info.allergies,info.app);         
                                 
                        printf("\n\n\t\t\t   NAME: ");
                        fflush(stdin);
                        gets(info.Name);     
     
                        printf("\n\n\t\t\t  ADDRESS: ");
                        gets(info.address);
     
                        printf("\n\n\t\t\t  NUMBER: ");
                        gets(info.number);
     
                        printf("\n\n\t\t\t  TREATMENT: ");
                        gets(info.treatment);
     
                        printf("\n\n\t\t\t  ALLERGIES: ");
                        gets(info.allergies); 
     
                        printf("\n\n\t\t\t  DATE OF BIRTH 12/12/12: "); 
                        gets(info.dob);     
        
                        printf("\n\n\t\t\t  DATE OF LAST APPOINTMENT 12/12/12: ");
                        gets(info.app);   
                        
                        
                        fseek(customer1,sizeof(info),SEEK_SET);
                        
                        fprintf(customer1,"%s %s %s %s %s %s %s %s ",info.regis,info.Name,info.address,info.number,info.dob,info.treatment,info.allergies,info.app);
                        
                        printf("\n\n\t\t  THE DETAILS OF THE ITEM HAS BEEN UPDATED SUCCESSFULLY");                     
                       
                       }
                        else if(!Found)
                         printf("\n\n\t\t THERES NO SUCH RECORD");
                       }
           
          
             
         }
       
        
     
  
      fclose(customer1);             
     
                       
     }

c

4 Contributors
5 Replies
124 Views
1 Day Discussion Span
Latest Post 14 Years Ago Latest Post by Ancient Dragon

All 5 Replies

Ancient Dragon 5,243 Achieved Level 70

14 Years Ago

why are you opening the same file twice (lines 11 and 22) ?

fseek() does not work well with text files.

Salem 5,138 Posting Sage

14 Years Ago

Interesting, how to be ignored in several places at once.
http://forums.devshed.com/c-programming-42/fseek-and-overwriting-data-683629.html

> p.s. Someone else can describe the common gotchas in your code. I'm a little lazy right now.
About half of this site should cover it ;)
http://sourceforge.net/apps/mediawiki/cpwiki/index.php?title=Main_Page

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Narue 5,707 Bad Cop Team Colleague · Answer 1 · 2010-03-10T20:02:41+00:00

>fseek() does not work well with text files.
More specifically, random offset access using fseek isn't guaranteed to be meaningful on text files. On a text file, you need to get some position indicators with ftell first, otherwise you're limited to boring stuff like seeking to the beginning of the file.

p.s. Someone else can describe the common gotchas in your code. I'm a little lazy right now.

donelliewhyte -7 Newbie Poster · Answer 2 · 2010-03-11T04:13:26+00:00

Thanks for your help so far that i have achieved my goal.

My other problem is updating a particular record using fseek()

void updaterecord(void)
{
     
   system("color 2");
   
   struct custinfo info;
   
   FILE *customer1;   
    
   
   customer1=fopen("customer1.txt","r");
   
   if (customer1==NULL)
            printf("\n\n\t\t\t  FILE WAS NOT FOUND ");
    else
         {
              char choice4; 
              char Target[50];
              int Found=0;
              
              
              if((customer1=fopen("customer1.txt","r"))==NULL)
                   printf("THE FILE IS EMPTY");
              else
              {
                  printf("\n\n\t\t ENTER ID NUM:");
                  scanf("%s",&Target);
                  while(!feof(customer1)&& Found==0)
                      {
                                    
                        fscanf(customer1,"%s %s %s %s %s %s %s %s",info.regis,info.Name,info.address,info.number,info.dob,info.treatment,info.allergies,info.app);
               
                        if(strcmp(Target,info.regis)==0)
                        Found=1;
                      }
                     
                      if(Found)
                      {                                              
                           
                        printf("\n\t\t  REGISTRATION:%s\n",info.regis);
                        printf("\n\t\t  NAME:%s\n",info.Name);
                        printf("\n\t\t  ADDRESS:%s\n",info.address);
                        printf("\n\t\t  NUMBER:%s\n",info.number);                       
                        printf("\n\t\t  DATE OF BIRTH:%s\n",info.dob); 
                        printf("\n\t\t  LAST TREATMENT:%s\n",info.treatment); 
                        printf("\n\t\t  ALLERGIES:%s\n",info.allergies);    
                        printf("\n\t\t  LAST APPOINTMENT:%s\n",info.app); 
                        
                        rewind(customer1);

                        fseek(customer1,sizeof(info),SEEK_SET);

                        fscanf(customer1,"%s %s %s %s %s %s %s %s",info.regis,info.Name,info.address,info.number,info.dob,info.treatment,info.allergies,info.app);         
                                 
                        printf("\n\n\t\t\t   NAME: ");
                        fflush(stdin);
                        gets(info.Name);     
     
                        printf("\n\n\t\t\t  ADDRESS: ");
                        gets(info.address);
     
                        printf("\n\n\t\t\t  NUMBER: ");
                        gets(info.number);
     
                        printf("\n\n\t\t\t  TREATMENT: ");
                        gets(info.treatment);
     
                        printf("\n\n\t\t\t  ALLERGIES: ");
                        gets(info.allergies); 
     
                        printf("\n\n\t\t\t  DATE OF BIRTH 12/12/12: "); 
                        gets(info.dob);     
        
                        printf("\n\n\t\t\t  DATE OF LAST APPOINTMENT 12/12/12: ");
                        gets(info.app);   
                        
                        
                        fseek(customer1,sizeof(info),SEEK_SET);
                        
                        fprintf(customer1,"%s %s %s %s %s %s %s %s ",info.regis,info.Name,info.address,info.number,info.dob,info.treatment,info.allergies,info.app);
                        
                        printf("\n\n\t\t  THE DETAILS OF THE ITEM HAS BEEN UPDATED SUCCESSFULLY");                     
                       
                       }
                        else if(!Found)
                         printf("\n\n\t\t THERES NO SUCH RECORD");
                       }
           
          
             
         }
       
        
     
  
      fclose(customer1);             
     
                       
     }

How would it be implemented if i changed the the file form text to another

Ancient Dragon 5,243 Achieved Level 70 Team Colleague Featured Poster · Answer 3 · 2010-03-11T11:19:43+00:00

If the customer structure does not contain any pointers then you could write the file out in binary mode so that fseek() to any given record position would be possible. Something like fwrite(fp, &Customer, 1, sizeof(struct customer)); Then read it back the same way but using fread() instead of fwrite().

fseek()

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