Mitme faili korraga kasutamine

Antud näitekood loeb andmefailist järjest ridu ning juhul kui tuvastab õpilase, kes sai 5, salvestab selle teise faili.

Andmefaili sisu formaadiga <nimi> <hinne>

Marju 4
Olga 5
Toomas 3
Helen 2
Peeter 5
Albert 4
Madis 5

Marju 4

Olga 5

Toomas 3

Helen 2

Peeter 5

Albert 4

Madis 5

Märka programmis järgnevat:

Enne teist andmefaili ei avata kui esimese avanemises on veendutud
Kui väljundfaili avamine ebaõnnestub, suletakse esmalt sisendfail ning alles seejärel sulgetakse programm
Märka ka, et antud programm on tundlik puhvri ületäitumise rünnakutele (pole selle näite raames oluline)

/**
 * File:        grades.c
 * Author:      Risto Heinsar
 * Created:     12.02.2015
 * Modified:    12.08.2024
 *
 * Description: Sample code using multiple file pointers at the same time.
 *              It finds the students who got 5 as the grade for the subject
 *              and outputs it to another file.
 */

#include <stdio.h>
#include <stdlib.h>

/* Names of files */
#define F_INPUT "grades.txt"
#define F_OUTPUT "fivers.txt"

/* Exit failure codes */
#define EXIT_INPUT_FAIL -1
#define EXIT_OUTPUT_FAIL -2

/* Name buffer length */
#define NAME_LEN 128

int main(void)
{
    /* Declare file pointer and attempt to open a file */
    FILE *fi = fopen(F_INPUT, "r");
    
    /* Check if it was opened successfully */
    if (fi == NULL)
    {
        printf("Error opening input file \"%s\"\n", F_INPUT);
        exit(EXIT_INPUT_FAIL);
    }
    
    /* Open and check for output file */
    FILE *fo = fopen(F_OUTPUT, "w");
    if (fo == NULL)
    {
        printf("Error opening output file\"%s\"\n", F_OUTPUT);
        
        /* Since fi was opened, we need to close it before exit */
        fclose(fi);
        exit(EXIT_OUTPUT_FAIL);
    }
    
    int grade;
    char name[NAME_LEN];
    /* Read the names and grades */
    while (fscanf(fi, "%s %d", name, &grade) == 2)
    {
        if (grade == 5)
        {
            fprintf(fo, "%s %d\n", name, grade);
        }
    }

    /* Close the files before exiting */
    fclose(fi);
    fclose(fo);
    
    return EXIT_SUCCESS;
}

/**

* File: grades.c

* Author: Risto Heinsar

* Created: 12.02.2015

* Modified: 12.08.2024

* Description: Sample code using multiple file pointers at the same time.

* It finds the students who got 5 as the grade for the subject

* and outputs it to another file.

#include <stdio.h>

#include <stdlib.h>

/* Names of files */

#define F_INPUT "grades.txt"

#define F_OUTPUT "fivers.txt"

/* Exit failure codes */

#define EXIT_INPUT_FAIL -1

#define EXIT_OUTPUT_FAIL -2

/* Name buffer length */

#define NAME_LEN 128

int main(void)

{

/* Declare file pointer and attempt to open a file */

FILE *fi = fopen(F_INPUT, "r");

/* Check if it was opened successfully */

if (fi == NULL)

{

printf("Error opening input file \"%s\"\n", F_INPUT);

exit(EXIT_INPUT_FAIL);

}

/* Open and check for output file */

FILE *fo = fopen(F_OUTPUT, "w");

if (fo == NULL)

{

printf("Error opening output file\"%s\"\n", F_OUTPUT);

/* Since fi was opened, we need to close it before exit */

fclose(fi);

exit(EXIT_OUTPUT_FAIL);

}

int grade;

char name[NAME_LEN];

/* Read the names and grades */

while (fscanf(fi, "%s %d", name, &grade) == 2)

{

if (grade == 5)

{

fprintf(fo, "%s %d\n", name, grade);

}

/* Close the files before exiting */

fclose(fi);

fclose(fo);

return EXIT_SUCCESS;

}