2-12

C Crash Course/21 Input&Output/prelesson/binary file/fwrite/student information/read.c

@@ -0,0 +1,45 @@
+#include<stdio.h>
+#include"student.h"
+
+void read(FILE* fp, int index);
+
+int main(void) {
+
+	FILE* fp = fopen("student.data", "r");
+	if (fp) {
+		fseek(fp, 0L, SEEK_END);//将文件读/写开始的位置定到结尾
+		long size = ftell(fp);//获得从文件开始到文件结尾的字节数
+		int index = 0;
+		int number = size / sizeof(Student);
+		printf("有 %d 个学生数据，你要看第几个\n", number);
+		scanf("%d", &index);
+		read(fp, index - 1);
+	}
+	else
+		printf("文件打开失败！\n");
+}
+
+void read(FILE* fp, int index) {
+
+	fseek(fp, index * sizeof(Student), SEEK_SET);
+
+	Student stu;
+
+	if (fread(&stu, sizeof(Student), 1, fp) == 1) {
+		printf("第 %d 个学生：\n", index + 1);
+		printf("\t姓名：%s\n", stu.name);
+		printf("\t性别：");
+		switch (stu.gender) {
+		case 0:
+			printf("男\n");
+			break;
+		case 1:
+			printf("女\n");
+			break;
+		default:
+			printf("其他\n");
+			break;
+		}
+		printf("\t年龄：%d\n", stu.age);
+	}
+}

C Crash Course/21 Input&Output/prelesson/binary file/fwrite/student information/write.c

@@ -52,7 +52,7 @@ void getList(Student* Stu, int num) {
 int save(Student* Stu, int num) {
 
 	int ret = -1;
-	FILE* fp = fopen("student.data", "wx");
+	FILE* fp = fopen("student.data", "wx");//如果要向student.data反复写入数据，将 wx 改为 x
 	if (fp) {
 		ret = fwrite(Stu, sizeof(Student), num, fp);
 		//记录 fwrite 的返回值：写入文件的学生个数