How to save into file ?

This is a discussion on How to save into file ? within the C Programming forums, part of the General Programming Boards category; For example : Code: struct record { char name[20]; float height; float weight; }; struct record RecArray[1000]; How can i ...

  1. #1
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    How to save into file ?

    For example :


    Code:
    struct record {
       char name[20];
       float height;
       float weight;
    };
    
    struct record RecArray[1000];
    How can i save into file call "record.dat" ?
    And how i can load from it ?

    If the question become like this, then i know how to save and load (Since 'struct record Rec' there are no array ):
    Code:
    struct record {
       char name[20];
       float height;
       float weight;
    };
    
    struct record Rec;
    so can somebody tell me how can i save it ?
    Thanks

  2. #2
    Even death may die... Dante Shamest's Avatar
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    EDIT:
    Crud, I just noticed that this is the C forum. Er, just use standard fopen, fclose and fwrite instead of the streams.

    Here's an example that works with 3 records, instead of 1000, but the principle is the same. Note also I have not done any error checking to keep the code shorter.

    Code:
    #include <iostream>
    #include <fstream>
    #include <stdlib.h>
    
    struct record {
       char name[20];
       float height;
       float weight;
    };
    
    int main(int argc, char *argv[])
    {
      // Array of 3 records.
      struct record RecArray[3];
    
      // Fill in 1st record information
      strcpy(RecArray[0].name,"Record 1") ;
      RecArray[0].height = 1.0 ;
      RecArray[0].weight = 1.0 ;
    
      // Fill in 2nd record information
      strcpy(RecArray[1].name,"Record 2") ;
      RecArray[1].height = 2.0 ;
      RecArray[1].weight = 2.0 ;
    
      // Fill in 3rd record information
      strcpy(RecArray[2].name,"Record 3") ;
      RecArray[2].height = 3.0 ;
      RecArray[2].weight = 3.0 ;
      
      // Save all the records into a file.
      std::ofstream out( "records.dat" ) ;
      for( int i=0; i<3; i++ )
        out.write( reinterpret_cast<char*>(&RecArray[i]), sizeof(record) ) ;
      out.close() ;
      
      // Read the SECOND record from the file.
      std::ifstream in( "records.dat" ) ;
      record tempRecord ;
      in.seekg( 1*sizeof(record) ) ;
      in.read( reinterpret_cast<char*>(&tempRecord), sizeof(record) ) ;
      in.close() ;
      
      // Print out details of 2nd record.
      std::cout << "Record name:   " << tempRecord.name << "\n" ;
      std::cout << "Record height  " << tempRecord.height << "\n" ;
      std::cout << "Record weight: " << tempRecord.weight << "\n" ;
      
      std::cin.get() ;
      return 0;
    }
    Last edited by Dante Shamest; 11-14-2003 at 11:18 PM.

  3. #3
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    For standard i know it can be save and load by this way :

    Code:
    struct record {
       char name[20];
       float height;
       float weight;
    };
    
    struct record Rec;
    Code:
    /* save into file */
    fwrite(&Rec, sizeof(struct record), 1, fptr1);
    Code:
    fread(&Rec, sizeof(Rec), 1, fptr1);
    while (!feof(fptr1)) {
       printf("%s", Rec.name);
       printf("%f", Rec.height);
       printf("%f", Rec.weight);
       printf("\n");
       /* read next record */
       fread(&Rec, sizeof(Rec), 1, fptr1);
    But when the structure contain of array, i dunno how to do it :/

    Code:
    struct record {
       char name[20];
       float height;
       float weight;
    };
    
    struct record RecArray[1000];

  4. #4
    and the hat of int overfl Salem's Avatar
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    > But when the structure contain of array, i dunno how to do it :/
    Same way

    /* write the whole array */
    n = fwrite( RecArray, 1000, sizeof(struct record), fp );
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  5. #5
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    how to write record one by one ?
    not understand at all >.<

  6. #6
    and the hat of int overfl Salem's Avatar
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    So write &recarray[i]
    and use a for loop

    But if you're just going to write the whole array you may as well write it all in one call
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  7. #7
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    Can give an example pseudocodes ?
    So blur now ~
    >.<

  8. #8
    and the hat of int overfl Salem's Avatar
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    And what pseudo-code could you possibly imagine for ONE line of code?

    You haven't even tried it yet have you
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

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