Help with file processing problem

Question

fddrummer06 0 Newbie Poster

15 Years Ago

I'm working on a problem in the File Processing chapter of my C book, and I've run into a few problems. I'm sure they are probably minor but I've been playing for a while and can't figure out why they are happening.

First: When printing a text file containing the information, the last item is always printed twice. This is around line 47

Second: when using option 2 to update a record, the name of the record updates fine but the quantity and cost do not. This part starts at line 90

Any help would be appreciated. Thanks.

[LIST=1]
[*]#include <stdlib.h>
[*]#include <stdio.h>
[*]#include<string.h>

[*]struct hardwareData { 
[*]   int RecordNum;         
[*]   char ToolName[ 15 ];  
[*]   int quantity;
[*]   double cost;       
[*]}; 


[*]int enterChoice( void );
[*]void textFile( FILE *readPtr );
[*]void updateRecord( FILE *fPtr );
[*]void newRecord( FILE *fPtr );
[*]void deleteRecord( FILE *fPtr );

[*]int main( void )
[*]{ 
[*]   FILE *cfPtr; 
[*]   int choice;  

[*]  
[*]   if ( ( cfPtr = fopen( "hardware.dat", "rb+" ) ) == NULL ) {
[*]      printf( "File could not be opened.\n" );
[*]   } 
[*]   else { 

[*]     
[*]      while ( ( choice = enterChoice() ) != 5 ) { 

[*]         switch ( choice ) { 

[*]           
[*]            case 1:
[*]               textFile( cfPtr );
[*]               break;

[*]          
[*]            case 2:
[*]               updateRecord( cfPtr );
[*]               break;

[*]           
[*]            case 3:
[*]               newRecord( cfPtr );
[*]               break;

[*]            
[*]            case 4:
[*]               deleteRecord( cfPtr );
[*]               break;
[*]         
[*]            
[*]            default:
[*]               printf( "Incorrect choice\n" );
[*]               break;
[*]       
[*]         }

[*]      } 

[*]      fclose( cfPtr ); 
[*]   } 
[*] 
[*] system("PAUSE");
[*]   return 0; 

[*]} 


[*]void textFile( FILE *readPtr )
[*]{ 
[*]   FILE *writePtr; 
[*]  
[*]   struct hardwareData hardware = { 0, "", 0, 0.0 };

[*]  
[*]   if ( ( writePtr = fopen( "hardware_list.txt", "w" ) ) == NULL ) {
[*]      printf( "File could not be opened.\n" );
[*]   } 
[*]   else { 
[*]      rewind( readPtr ); 
[*]      fprintf( writePtr, "%-12s%-20s%-11s%10s\n", 
[*]         "Record #", "Tool Name", "Quantity","Cost" );

[*]      
[*]      while ( !feof( readPtr ) ) { 
[*]         fread( &hardware, sizeof( struct hardwareData ), 1, readPtr );
[*]        
[*]        
[*]         if ( hardware.RecordNum != 0 ) {
[*]            fprintf( writePtr, "%-12d%-20s%-11d%10.2f\n",
[*]               hardware.RecordNum, hardware.ToolName,
[*]               hardware.quantity, hardware.cost );

[*]          } 

[*]      } 

[*]      fclose( writePtr ); 
[*]   } 

[*]} 

[*]void updateRecord( FILE *fPtr )
[*]{ 
[*]   int record;        
[*]   int newquantity=0; 
[*]   int newcost=0;
[*]   char NewToolName[18];


[*]   
[*]   struct hardwareData hardware = { 0, "", 0, 0.0 };

[*]  
[*]   printf( "Enter record to update ( 1 - 100 ): " );
[*]   scanf( "%d", &record );

[*]   
[*]   fseek( fPtr, ( record - 1 ) * sizeof( struct hardwareData ), 
[*]      SEEK_SET );

[*]   
[*]   fread( &hardware, sizeof( struct hardwareData ), 1, fPtr );

[*]   
[*]   if ( hardware.RecordNum == 0 ) {
[*]      printf( "Record #%d has no information.\n", record );
[*]   } 
[*]   else { 
[*]   
[*]      printf( "%-12s%-20s%-11s%10s\n", 
[*]         "Record #", "Tool Name", "Quantity","Cost" );
[*]      printf( "%-12d%-20s%-11d%10.2f\n\n", 
[*]               hardware.RecordNum, hardware.ToolName,
[*]               hardware.quantity, hardware.cost );
[*]      
[*]      
[*]      printf( "Enter new tool name (without spaces), Quantity, and Cost: " );
[*]      scanf( "%s%d%lf", &NewToolName, &newquantity, &newcost );

[*]    
[*]      hardware.quantity = newquantity;
[*]      hardware.cost = newcost;
[*]      strcpy(hardware.ToolName, NewToolName);
[*]    
[*]          printf( "%-12s%-20s%-11s%10s\n", 
[*]         "Record #", "Tool Name", "Quantity","Cost" );
[*]         
[*]      printf( "%-12d%-20s%-11d%10.2f\n", 
[*]               hardware.RecordNum, hardware.ToolName,
[*]               hardware.quantity, hardware.cost );
[*]      
[*]      
[*]      fseek( fPtr, ( record - 1 ) * sizeof( struct hardwareData ), 
[*]         SEEK_SET );


[*]      
[*]      
[*]      fwrite( &hardware, sizeof( struct hardwareData ), 1, fPtr );
[*]   } 

[*]}



[*]/* delete an existing record */
[*]void deleteRecord( FILE *fPtr )
[*]{ 

[*]   struct hardwareData hardware; 
[*]   struct hardwareData blankHardware = { 0, " ", 0, 0 }; 
[*]   
[*]   int RecordNum; 

[*]   
[*]   printf( "Enter record number to delete ( 1 - 100 ): " );
[*]   scanf( "%d", &RecordNum );

[*]   
[*]   fseek( fPtr, ( RecordNum - 1 ) * sizeof( struct hardwareData ), 
[*]      SEEK_SET );

[*]   
[*]   fread( &hardware, sizeof( struct hardwareData ), 1, fPtr );

[*]  
[*]   if ( hardware.RecordNum == 0 ) {
[*]      printf( "Record %d does not exist.\n", RecordNum );
[*]   } 
[*]   else { 

[*]      
[*]      fseek( fPtr, ( RecordNum - 1 ) * sizeof( struct hardwareData ), 
[*]         SEEK_SET );

[*]      
[*]      fwrite( &blankHardware, 
[*]         sizeof( struct hardwareData ), 1, fPtr );
[*]   }

[*]}



[*]/*create new record*/
[*]void newRecord( FILE *fPtr )
[*]{ 
[*]   
[*]   struct hardwareData hardware = { 0, "", 0, 0.0 };

[*]   int RecordNum; 

[*]  
[*]   printf( "Enter new record number ( 1 - 100 ): " );
[*]   scanf( "%d", &RecordNum );

[*]   
[*]   fseek( fPtr, ( RecordNum - 1 ) * sizeof( struct hardwareData ), 
[*]      SEEK_SET );

[*]   
[*]   fread( &hardware, sizeof( struct hardwareData ), 1, fPtr );

[*]   
[*]   if ( hardware.RecordNum != 0 ) {
[*]      printf( "Account #%d already contains information.\n",
[*]              hardware.RecordNum );
[*]   } 
[*]   else { 

[*]      
[*]      printf( "Enter tool name (without spaces), quantity, cost\n? " );
[*]      scanf( "%s%d%lf", &hardware.ToolName, &hardware.quantity, 
[*]         &hardware.cost );

[*]      hardware.RecordNum = RecordNum;
[*]      
[*]      
[*]      fseek( fPtr, ( hardware.RecordNum - 1 ) * 
[*]         sizeof( struct hardwareData ), SEEK_SET );

[*]      
[*]      fwrite( &hardware, 
[*]         sizeof( struct hardwareData ), 1, fPtr );
[*]   } 

[*]} 
[*]int enterChoice( void )
[*]{ 
[*]   int menuChoice;


[*]   printf( "\nEnter your choice\n"
[*]      "1 - store a formatted text file of acounts called\n"
[*]      "    \"hardware_list.txt\" for printing\n"
[*]      "2 - update a record\n"
[*]      "3 - add a new record\n"
[*]      "4 - delete a record\n"
[*]      "5 - end program\n? " );

[*]   scanf( "%d", &menuChoice ); 

[*]   return menuChoice;
[/LIST]

}

c

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Latest Post 15 Years Ago Latest Post by fddrummer06

All 6 Replies

Salem 5,138 Posting Sage

15 Years Ago

http://faq.cprogramming.com/cgi-bin/smartfaq.cgi?answer=1046476070&id=1043284351
Test the result of the read operation.
EOF is a state set after the event, not a prediction of the future.

Eg. while ( fread( &hardware, sizeof( struct hardwareData ), 1, readPtr ) == 1 )

Salem 5,138 Posting Sage

15 Years Ago

Now remove the fread() which is inside the loop (line 13)

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fddrummer06 0 Newbie Poster · Answer 1 · 2008-07-16T21:06:25+00:00

I've tried both the line you posted as well as modifying what is in the post on the FAQ, but I am still getting the last line twice.

Any idea on why I am unable to update a record? Lets say, for example, I have the following information in the file.

Record number 1
Tool name: Tool1
Quantity: 7
Cost: 1.99

When I run the update portion of the program, I can change the name, but no matter what i enter for the quantity and cost, printing the text file lists the quantity as 1074266112 and the cost as 0.00

Salem 5,138 Posting Sage · Answer 2 · 2008-07-16T21:53:17+00:00

Maybe post what you changed it to, rather than just describing the delta.
More often than not, you haven't done it.

fddrummer06 0 Newbie Poster · Answer 3 · 2008-07-16T22:22:08+00:00

Here I've taken the while statement in your post and replaced mine with it (line 12). Maybe I'm not quite understanding the concept, but from what I got out of the FAQ post and your post, this is how I see it.

[LIST=1]
[*]void textFile( FILE *readPtr )
[*]{ 
[*]   FILE *writePtr; 
[*]  
[*]   struct hardwareData hardware = { 0, "", 0, 0.0 };

[*]  
[*]   if ( ( writePtr = fopen( "hardware_list.txt", "w" ) ) == NULL ) {
[*]      printf( "File could not be opened.\n" );
[*]   } 
[*]   else { 
[*]      rewind( readPt
r ); 
[*]      fprintf( writePtr, "%-12s%-20s%-11s%10s\n", 
[*]         "Record #", "Tool Name", "Quantity","Cost" );

[*]      
[*]      while ( fread( &hardware, sizeof( struct hardwareData ), 1, readPtr ) == 1 ){ 
[*]            
[*]         fread( &hardware, sizeof( struct hardwareData ), 1, readPtr );
[*]        
[*]   
[*]        if (hardware.RecordNum != 0){
[*]            fprintf( writePtr, "%-12d%-20s%-11d%10.2f\n",
[*]               hardware.RecordNum, hardware.ToolName,
[*]               hardware.quantity, hardware.cost );

[*]               }
[*]               }

[*]      } 

[*]       fclose( writePtr );
[*]       
[*]   }
[/LIST]

fddrummer06 0 Newbie Poster · Answer 4 · 2008-07-16T22:45:19+00:00

fddrummer06 0 Newbie Poster

15 Years Ago

Simple enough, works just fine now. Thanks!

Help with file processing problem

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