C程序设计 （第四版） 谭浩强 习题10.10

习题10.10 从第9题的“职工工资文件”中删除一个职工的数据，再存回原文件。

IDE工具：VS2010

Note: 使用不同的IDE工具可能有部分差异。

 

代码块

方法：使用指针，函数的模块化设计，动态分配内存

说明：文件wage.dat已经存在与项目目录下。

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

#define N 3

typedef struct{
	int num;
	char name[20];
	char gender;
	int age;
	char addr[20];
	float wage;
	char health;
	char edu[10];
}Employee;

void initialVar(Employee **emp, int n, char **name){
	*emp = (Employee*)malloc(n * sizeof(Employee));
	*name = (char*)malloc(80 * sizeof(char));
}

void inputFileName(FILE **file, char *name){
	printf("Enter File Name: ");
	scanf("%s", name);

	*file = fopen(name, "rb");
	if(*file == NULL){
		perror("Cannot open this file");
		system("pause");
		exit(0);
	}
}

void readFile(FILE **file, Employee *emp, int n){
	printf("Read File Info:\n");
	for(int i = 0; i < n; i++){
		fread(&emp[i].name, sizeof(Employee), 1, *file);
		fread(&emp[i].wage, sizeof(Employee), 1, *file);
		printf("Name: %-10s  Wage: %-.2f\n", emp[i].name, emp[i].wage);
	}
	printf("\n");
	fclose(*file);
}

void deleteRec(FILE **file, char *name, Employee *emp, int n, int num){
	for(int i = 0; i < n; i++){
		if(i == num - 1){
			for(int j = i; j < n - 1; j++){
				emp[j] = emp[j+1];
			}
			break;
		}
	}

	*file = fopen(name, "wb");
	if(*file == NULL){
		perror("Cannot open this file");
		system("pause");
		exit(0);
	}

	for(int i = 0; i < n - 1; i++){
		if(fwrite(&emp[i].name, sizeof(Employee), 1, *file) != 1){
			perror("File Write Error");
			system("pause");
			exit(0);
		}	
		if(fwrite(&emp[i].wage, sizeof(Employee), 1, *file) != 1){
			perror("File Write Error");
			system("pause");
			exit(0);
		}
	}
	fclose(*file);
}

void outputFileNew(FILE **file, char *name, Employee *emp, int n){
	*file = fopen(name, "rb");
	if(*file == NULL){
		perror("Cannot open this file");
		system("pause");
		exit(0);
	}

	printf("New Employee Info:\n");
	for(int i = 0; i < n; i++){
		fread(&emp[i].name, sizeof(Employee), 1, *file);
		fread(&emp[i].wage, sizeof(Employee), 1, *file);
		printf("Name: %-10s  Wage: %-.2f\n", emp[i].name, emp[i].wage);
	}
	printf("\n");
	fclose(*file);
}

int main(){
	FILE *file = NULL;
	Employee *emp = NULL;
	char *name = NULL;

	initialVar(&emp, N, &name);
	inputFileName(&file, name);
	readFile(&file, emp, N);
	deleteRec(&file, name, emp, N, 1);
	outputFileNew(&file, name, emp, N-1);
	
	system("pause");
	return 0;
}

运行结果如下：