File Handling Example
/* File handling example for PR101 */
/* processing an ASCII file of records */
/* Written by B. Brown, April 1994 */
/* process a goods file, and print out */
/* all goods where the quantity on */
/* hand is less than or equal to the */
/* re-order level. */
#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include <stdlib.h>
/* definition of a record of type goods */
struct goods {
char name[20]; /* name of product */
float price; /* price of product */
int quantity; /* quantity on hand */
int reorder; /* re-order level */
};
/* function prototypes */
void myexit( int );
void processfile( void );
void printrecord( struct goods );
int getrecord( struct goods * );
/* global data variables */
FILE *fopen(), *input_file; /* input file pointer */
/* provides a tidy means to exit program gracefully */
void myexit( int exitcode )
{
if( input_file != NULL )
fclose( input_file );
exit( exitcode );
}
/* prints a record */
void printrecord( struct goods record )
{
printf("\nProduct name\t%s\n", record.name );
printf("Product price\t%.2f\n", record.price );
printf("Product quantity\t%d\n", record.quantity );
printf("Product reorder level\t%d\n", record.reorder );
}
/* reads one record from inputfile into 'record', returns 1 for success */
int getrecord( struct goods *record )
{
int loop = 0, ch;
char buffer[40];
ch = fgetc( input_file );
/* skip to start of record */
while( (ch == '\n') || (ch == ' ') && (ch != EOF) )
ch = fgetc( input_file );
if( ch == EOF ) return 0;
/* read product name */
while( (ch != '\n') && (ch != EOF)) {
buffer[loop++] = ch;
ch = fgetc( input_file );
}
buffer[loop] = 0;
strcpy( record->name, buffer );
if( ch == EOF ) return 0;
/* skip to start of next field */
while( (ch == '\n') || (ch == ' ') && (ch != EOF) )
ch = fgetc( input_file );
if( ch == EOF ) return 0;
/* read product price */
loop = 0;
while( (ch != '\n') && (ch != EOF)) {
buffer[loop++] = ch;
ch = fgetc( input_file );
}
buffer[loop] = 0;
record->price = atof( buffer );
if( ch == EOF ) return 0;
/* skip to start of next field */
while( (ch == '\n') || (ch == ' ') && (ch != EOF) )
ch = fgetc( input_file );
if( ch == EOF ) return 0;
/* read product quantity */
loop = 0;
while( (ch != '\n') && (ch != EOF)) {
buffer[loop++] = ch;
ch = fgetc( input_file );
}
buffer[loop] = 0;
record->quantity = atoi( buffer );
if( ch == EOF ) return 0;
/* skip to start of next field */
while( (ch == '\n') || (ch == ' ') && (ch != EOF) )
ch = fgetc( input_file );
if( ch == EOF ) return 0;
/* read product reorder level */
loop = 0;
while( (ch != '\n') && (ch != EOF)) {
buffer[loop++] = ch;
ch = fgetc( input_file );
}
buffer[loop] = 0;
record->reorder = atoi( buffer );
if( ch == EOF ) return 0;
return 1; /* signify record has been read successfully */
}
/* processes file for records */
void processfile( void )
{
struct goods record; /* holds a record read from inputfile */
while( ! feof( input_file )) {
if( getrecord( &record ) == 1 ) {
if( record.quantity <= record.reorder )
printrecord( record );
}
else myexit( 1 ); /* error getting record */
}
}
main()
{
char filename[40]; /* name of database file */
printf("Example Goods Re-Order File Program\n");
printf("Enter database file ");
scanf(" %s", filename );
input_file = fopen( filename, "rt" );
if( input_file == NULL ) {
printf("Unable to open datafile %s\n", filename );
myexit( 1 );
}
processfile();
myexit( 0 );
}
Please obtain the data file for this example from your tutor, or via ftp.
©Copyright B Brown. 1984-1999. All rights reserved.