8.5 文件IO fgets fputs fgetc fwrite fread

int main()
{
	FILE *fp, *fpcp;
	fp = fopen("yesteday_once_more.txt", "r");
	fpcp = fopen("a", "w");
	char buf[1024];			//一行给他1024个字节 尽量够用
	while (fgets(buf, sizeof(buf), fp) != NULL)
	{
		fputs(buf, fpcp);
	}
	fclose(fp);
	fclose(fpcp);
	return 0;
}

#include <stdio.h>
int main()
{
        FILE *fp;
        fp = fopen("record", "a+");
        char buf[10];
        while (fgets(buf, sizeof(buf), stdin) != NULL)
        {
                fputs(buf,stdout);
                fputs(buf, fp);     //linux下 ctrl+d才生效
        }
        fclose(fp);
        return 0;
}

int line(char * s)
{
	FILE *fp;
	fp = fopen(s, "r");
	char buf[1024];
	int n = 0;
	while (fgets(buf, sizeof(buf), fp) != NULL)
		n++;
	fclose(fp);
	return n;
}
int main()
{
	int n = line("yesteday_once_more.txt");
	printf("%d\n", n);
}

int len(char * s)
{
	FILE * fp;
	int n = 0;
	fp = fopen(s, "r");
	if (!fp)
		return -1;
	char ch;
	while ((ch = fgetc(fp)) != EOF)
		n++;
	fclose(fp);
	return n;
}
int main()
{
	int n = len("yes.txt");
	printf("%d\n", n);
	return 0;
}

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct STU
{
        int id;
        char name[20];
        char sex;
        int score;
} *pS;
int count_stu(FILE * fp)
{
        char buf[1024];
        int n = 0;
        while (fgets(buf, sizeof(buf), fp) != NULL)
                n++;
        rewind(fp);
        return n / 5;
}
int file_stu(FILE * fp, pS a, int n)
{
        int i = 0;
        char buf[1024];
        for (i = 0; i < n; i++)
        {
                fgets(buf, sizeof(buf), fp);
                a[i].id = atoi(buf);
                fgets(a[i].name, sizeof(a[i].name), fp);
                strtok(a[i].name, "\n");
                fgets(buf, sizeof(buf), fp);
                a[i].sex = buf[0];
                fgets(buf, sizeof(buf), fp);
                a[i].score = atoi(buf);
                fgets(buf, sizeof(buf), fp);
        }
        rewind(fp);
        return i;
}
void show_stu(pS a, int n)
{
        int i = 0;
        for (i = 0; i < n; i++)
        {
                printf("%d %s %c %d\n", a[i].id, a[i].name, a[i].sex, a[i].score);
        }
        printf("***************\n");
        return;
}
//此函数第一种写法
int stu_bin(FILE * fp, pS a, int n)
{
        fwrite(a, sizeof(*a), n, fp);
        rewind(fp);
        return 0;
}
//此函数第二种写法
int stu_bin(FILE *fp, pS a, int n)
{
        int i;
        for (i = 0; i < n; i++)
        {
                fwrite(&a[i], sizeof(a[i]), 1, fp);
        }
        rewind(fp);
        return i;
}
int bin_stu(FILE * fp, pS a, int n)
{
        fread(a, sizeof(*a), n, fp);
        rewind(fp);
        return 0;
}
int sort_by_id(pS a, pS b)
{
        return a->id - b->id;
}
int sort_by_name(pS a, pS b)
{
        return strcmp(a->name, b->name);
}
int sort_by_sex(pS a, pS b)
{
        return a->sex - b->sex;
}
int sort_by_score(pS a, pS b)
{
        return a->score - b->score;
}
void sort_stu(pS a, int n, int(*fun)(pS a, pS b))
{
        int i, j, min;
        struct STU temp;
        for (i = 0; i < n; i++)
        {
                min = i;
                for (j = i + 1; j < n; j++)
                {
                        if (fun(&a[min], &a[j])>0)
                        {
                                min = j;
                        }
                }
                temp = a[min];
                a[min] = a[i];
                a[i] = temp;
        }
        return;
}
int main(void)
{
        FILE * fp = fopen("stu.txt", "r");
        FILE * fp_bin = fopen("stu.bin", "w+");  //注意这里是w+，如果是w的话就不能读了，注意坑
        if (!fp || !fp_bin)
                return -1;
        int count = count_stu(fp);
        struct STU * a = (pS)malloc(count * sizeof(*a));
        file_stu(fp, a, count);
        //show_stu(a, count);
        stu_bin(fp_bin, a, count);
        memset(a, 0, (count * sizeof(*a)));
        bin_stu(fp_bin, a, count);
        fclose(fp);
        fclose(fp_bin);
        show_stu(a, count);
        sort_stu(a, count, sort_by_id);
        show_stu(a, count);
        sort_stu(a, count, sort_by_name);
        show_stu(a, count);
        sort_stu(a, count, sort_by_sex);
        show_stu(a, count);
        sort_stu(a, count, sort_by_score);
        show_stu(a, count);
        free(a);
}