Saving the Structure Contents in a File - C File

C examples for File:File Write

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Description

Saving the Structure Contents in a File

Demo Code

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAXTITL  40//  w w w.j  a  v  a2s .co m
#define MAXAUTL  40
#define MAXBKS   10             /* maximum number of books */
char * s_gets(char * st, int n);
struct book {                   /* set up book template    */
    char title[MAXTITL];
    char author[MAXAUTL];
    float value;
};

int main(void)
{
    struct book my[MAXBKS]; /* array of structures     */
    int count = 0;
    int index, filecount;
    FILE * pbooks;
    int size = sizeof (struct book);
    
    if ((pbooks = fopen("book.dat", "a+b")) == NULL) {
        fputs("Can't open book.dat file\n",stderr);
        exit(1);
    }
    
    rewind(pbooks);            /* go to start of file     */
    while (count < MAXBKS &&  fread(&my[count], size,1, pbooks) == 1)
    {
        if (count == 0)
            puts("Current contents of book.dat:");
        printf("%s by %s: $%.2f\n",my[count].title,
               my[count].author, my[count].value);
        count++;
    }
    filecount = count;
    if (count == MAXBKS) {
        fputs("The book.dat file is full.", stderr);
        exit(2);
    }
    
    puts("Press [enter] at the start of a line to stop.");
    while (count < MAXBKS && s_gets(my[count].title, MAXTITL) != NULL && my[count].title[0] != '\0')
    {
        puts("Now enter the author.");
        s_gets(my[count].author, MAXAUTL);
        puts("Now enter the value.");
        scanf("%f", &my[count++].value);
        while (getchar() != '\n')
            continue;                /* clear input line  */
        if (count < MAXBKS)
            puts("Enter the next title.");
    }
    
    if (count > 0)
    {
        puts("Here is the list of your books:");
        for (index = 0; index < count; index++)
            printf("%s by %s: $%.2f\n",my[index].title, my[index].author, my[index].value);
        fwrite(&my[filecount], size, count - filecount, pbooks);
    }
    fclose(pbooks);
    
    return 0;
}

char * s_gets(char * st, int n)
{
    char * ret_val;
    char * find;
    
    ret_val = fgets(st, n, stdin);
    if (ret_val)
    {
        find = strchr(st, '\n');   // look for newline
        if (find)                  // if the address is not NULL,
            *find = '\0';          // place a null character there
        else
            while (getchar() != '\n')
                continue;          // dispose of rest of line
    }
    return ret_val;
}

Result


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