Fájlkezelés alapok (bináris)

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

#define FILENAME "cd.bin"
#define FILENAME_TEMP "cd_temp.bin"

typedef struct cd{
    char cim[20];
    char eloado[20];
    int kiadas_eve;
    float ar;
} CD;

void feltolt(int db);
void listaz(void);
void keres(char *k_eloado);
void modosit(int kor);
void torol(float arhatar);

int main(void){
    int db;
    int kor;
    char keresett_eloado[20];
    float arhatar;

    printf("\nHany adatot szeretnel felvinni?");
    scanf("%d", &db);
    feltolt(db);
    listaz();

    printf("\nMelyik eloado cd-eit keresed?\n");
    scanf("%s", keresett_eloado);
    keres(keresett_eloado);

    printf("\n Melyik cd arat szeretned csokkenteni?");
    scanf("%d", &kor);
    modosit(kor);
    listaz();
    printf("\n Milyen arnal dragabb cd-ket torol?");
    scanf("%f", &arhatar);
    listaz();
    torol(arhatar);
    return 0;
}
void feltolt(int db){
    FILE *fp;
    int i;
    CD cd;

    fp = fopen(FILENAME, "ab");
    if(!fp) {printf("\nSikertelen fajl megnyitas."); return;}


    for(i=0; i<db; i++){
        printf("\n%d. CD cime: ", i+1); scanf("%s", cd.cim);
        printf("\n%d. CD eloadoja: ", i+1); scanf("%s", cd.eloado);
        printf("\n%d. CD kiadasi eve: ", i+1); scanf("%d", &cd.kiadas_eve);
        printf("\n%d. CD ara: ", i+1); scanf("%f", &cd.ar);
        fwrite(&cd, sizeof(CD), 1, fp);
    }
    fclose(fp);
    return;
}

void listaz(void){
    FILE *fp;
    int i;
    int filesize;
    CD cd;

    fp = fopen(FILENAME, "rb");
    if(!fp) {printf("Sikertelen fajl megnyitas."); return;}
    fseek(fp, 0, SEEK_END);
    filesize = ftell(fp)/sizeof(CD);

    for(i=0; i<filesize; i++){
        fseek(fp, sizeof(CD)*i, SEEK_SET);
        fread(&cd, sizeof(CD), 1, fp);
        printf("\n %d. CD cime: %s \t eloadoja: %s \t kiadasi eve: %d \t ara: %.2f,", i+1, cd.cim, cd.eloado, cd.kiadas_eve, cd.ar);
    }
    fclose(fp);
    return;

}

void keres(char *k_eloado){
    FILE *fp;
    int i;
    int filesize;
    CD cd;

    fp = fopen(FILENAME, "rb");
    if(!fp) {printf("Sikertelen fajl megnyitas."); return;}
    fseek(fp, 0, SEEK_END);
    filesize = ftell(fp)/sizeof(CD);

    for(i=0; i<filesize; i++){
        fseek(fp, sizeof(CD)*i, SEEK_SET);
        fread(&cd, sizeof(CD), 1, fp);
        if(strcmp(cd.eloado, k_eloado)==0){
            printf("\n %d. CD cime: %s \t eloadoja: %s \t kiadasi eve: %d \t ara: %.2f,", i+1, cd.cim, cd.eloado, cd.kiadas_eve, cd.ar);
        }
    }
    fclose(fp);
    return;
}

void modosit(int kor){
    FILE *fp;
    int i;
    int filesize;
    int nap;
    int ev;
    CD cd;
    char honap[4];

    fp = fopen(FILENAME, "rb+");
    if(!fp) {printf("Sikertelen fajl megnyitas."); return;}
    fseek(fp, 0, SEEK_END);
    filesize = ftell(fp)/sizeof(CD);
    sscanf(__DATE__, "%s %d %d", honap, &nap, &ev);

    for(i=0; i<filesize; i++){
        fseek(fp, sizeof(CD)*i, SEEK_SET);
        fread(&cd, sizeof(CD), 1, fp);
        if((ev-cd.kiadas_eve)>kor){
            cd.ar*=0.9;
            fseek(fp, sizeof(CD)*(-1), SEEK_CUR);
            fwrite(&cd, sizeof(CD), 1, fp);
        }
    }
    fclose(fp);
    return;
}

void torol(float arhatar){
    FILE *fp, *fp_temp;
    int i;
    int filesize;
    int deleted=0;
    CD cd;

    fp = fopen(FILENAME, "rb");
    if(!fp) {printf("Sikertelen fajl megnyitas."); return;}

    fp_temp = fopen(FILENAME_TEMP, "wb+");
    if(!fp_temp) {printf("Sikertelen fajl megnyitas."); return;}

    fseek(fp, 0, SEEK_END);
    filesize = ftell(fp)/sizeof(CD);

    for(i=0; i<filesize; i++){
        fseek(fp, sizeof(CD)*i, SEEK_SET);
        fread(&cd, sizeof(CD), 1, fp);
        if(cd.ar<=arhatar){
            fwrite(&cd, sizeof(CD), 1, fp_temp);
        }
        else{
            printf("\nTorolve %d. CD cime: %s \t eloadoja: %s \t kiadasi eve: %d \t ara: %.2f,", i+1, cd.cim, cd.eloado, cd.kiadas_eve, cd.ar);
            deleted++;
        }
    }
    printf("%d", deleted);
    fclose(fp);
    fp = fopen(FILENAME, "wb");

    if(!fp) {printf("Sikertelen fajl megnyitas."); return;}
    for(i=0; i<filesize-deleted; i++){
        fseek(fp_temp, sizeof(CD)*i, SEEK_SET);
        fread(&cd, sizeof(CD), 1, fp_temp);
        fwrite(&cd, sizeof(CD), 1, fp);
    }

    fclose(fp_temp);
    fclose(fp);
    return;
}