How can I do sort program for unsorted setup file?

[happy]

#include <stdio.h>
#include <conio.h>
/*TV Rental file Set_up -Version 01
-Setting up a file containing sutomer information*/
struct customer_record /*Defining a csutomer record*/
{
int customer_no;
int no_of_weeks;
char tv_type;
};
main ()
{
/*-------1-open file for output*/
struct customer_record customer;
FILE *fp_setup;
if ((fp_setup=fopen("setup.txt","w")) == NULL)
{
printf("\nCan not open file 'setup.txt' for writing \n");
printf("Program is termainted");
exit();
}
clrscr();

/*-------2-while more customers----------separate function-------*/
do {
/*-------2-1-input customers record------separate function-------*/
customer_input(&customer);
/*-------2-2-write customer record to file*/
fprintf(fp_setup,"%4d%2d%c\n",customer);
} while (another_customer()=='y');
/*-------3-write end of file record to file */
fprintf(fp_setup,"%4d%2d%c\n",9999,99,' ');
/*-------4-close file*/
fclose(fp_setup);
return 0;
}


customer_input(cust)
/*---------------------*/
struct customer_record *cust;
{
printf("\nEnter customer number :");
scanf("%4d",&(*cust).customer_no);
printf("\nEnter number of weeks rent due :");
scanf("%2d",&(*cust).no_of_weeks);
printf("Enter type of rental -c for colors TV");
printf("\n -b for black and white TV");
printf("\n -v for video");
printf("\n -o for other : ");
scanf("\n");
scanf("%c",&(*cust).tv_type);
}

another_customer()
/*----------------*/
{
char another;
printf("\nAnother new_screen_customer for input (y or n) : ");
scanf("\n");
scanf("%c",&another);
return (another);
}

 

[dandelion]

Asking a question *once* suffices.

Judging from your code, you'd be better off using some database (lib or
server). At least that takes care of all the hassle for you. Do not
needlessly reinvent wheels.

If you insist on doing all the sorting yourself you have a number of options
open:

A) read the file into an array and employ qsort(). This will not work for
very big files, since they
would not fit in memory.
B) Create an index by reading only those fields you are using as key, add
the record number,
employ qsort() and use the result as an index.
C) Consult Knuth "The art of computer programming Vol. III "Sorting and
Searching" Chapter 5,
section 4, which will give you a few good ways to do it.