把数据写入日志文件

实现代码一：

#include "stdio.h"
#include "malloc.h"
#include "string.h"
#include "stdlib.h"

#define N  28 /*每个成员的最大长度*/

typedef struct node
{
	char name[N];
	char value[N];
	struct node *next;
}node;


void print(struct node *head)
{
	struct node *p;
	p=head;
	if(p == NULL)
	{
		printf("Don't find the file !\n");
	}
	while(p != NULL)
	{
			printf("%s %s\n",p->name,p->value);
			p=p->next;
	}
}
void save(char*filename,struct node *head) 
{ 

          FILE* fp; 
          node *p; 
          int flag=1,count=0;
          /*为输出打开一个二进制的文件*/
          fp = fopen(filename,"w"); 
          if(fp == NULL) 
          {         
          	 printf("\n=====>提示:重新打开文件时发生错误!\n");                     
             exit(1);  
          } 
          /*将p连接在head的后面*/ 
         // p=head->next; //关键是有头指针，还是没有头指针
          p = head;
          /*判断p是否为空,以便进行循环*/
          while(p) 
          { 
          	/*把p中的内容写到fp中*/
            if(fwrite(p,sizeof(struct node)-4,1,fp)==1) 
			{ 
				p=p->next; /*p向后移动一*/
                count++;/*用于统计保存书籍记录的数目*/ 
             } 
             else/*如果fwrite(p,sizeof(struct book),1,fp)返回值不是一，提前跳出循环*/
             {        
	             	flag=0;            	     
	             	break; 
             } 
          }
          if(flag==1)
		  { 
                printf("\n=====>提示:文件保存成功.(有%d条记录已经保存).\n",count);  

          } 
          
         fclose(fp); //关闭fp文件

}

int main(int argc, char* argv[])
{
	struct node *head,*p[9];
	head = NULL;
	char *filename = "D://tianmo.txt";

	/*把修改的配置文件保存*/
	char * ip_addr = "1.1.1.1";
	char *netmask_addr = "2.2.2.2";
	char *brdaddr_addr = "3.3.3.3";
	char *mac_addr = "4.4.4.4";
	int i;
	for(i= 0;i < 9 ;i ++){
		p[i] = (node *)malloc(sizeof(node));
	}
	
	head = p[0];
	
    memset(p[0]->name,0,N);
	strcpy(p[0]->name  , "# Advanced Micro Devices[AM");//28
	p[0]->name[27] = '\0';
	memset(p[0]->value,0,N);
	strcpy(p[0]->value , "D] 79c970 [PCnet32 LANCE  \0");//28
	p[0]->value[27] = '\0';

	memset(p[1]->name,0,N);
	strcpy(p[1]->name  , "\nDEVICE=                 \0");
	p[1]->name[27] = '\0';	
	memset(p[1]->value,0,N);
	strcpy(p[1]->value,  "eth0                     \0 ");
	p[1]->value[27] = '\0';


	strcpy(p[2]->name ,  "\nBOOTPROT=                 ");
	p[2]->name[27] = '\0';
	strcpy(p[2]->value , "static                      ");
	p[2]->value[27] = '\0';

	strcpy(p[7]->name ,  "\nONBOOT=                   ");
	p[7]->name[27] = '\0';
	strcpy(p[7]->value,  "yes                         ");
	p[7]->value[27] = '\0';

	strcpy(p[8]->name ,  "\nTYPE=                     ");
	p[8]->name[27] = '\0';
	strcpy(p[8]->value,  "Ethernet                    ");
	p[8]->value[27] = '\0';

    memset(p[3]->name,0,N);
	strcpy(p[3]->name , "\nIPADDR=");
	p[3]->name[8] = '\0';
	memset(p[3]->value,0,N);
	for( i = 0;ip_addr[i] != '\0';i++)
		p[3]->value[i] = ip_addr[i];
	p[3]->value[i+1] = '\0';
	

    memset(p[4]->name,0,N);	
	strcpy(p[4]->name ,"\nNETMASK=");
	p[4]->name[9] = '\0';
	memset(p[4]->value,0,N);
	for( i = 0;netmask_addr[i] != '\0';i++)
		p[4]->value[i] = netmask_addr[i];
	p[4]->value[i+1] = '\0';


	memset(p[5]->name,0,N);	
	strcpy(p[5]->name , "\nGATEWAY=");
	p[5]->name[9] = '\0';
	memset(p[5]->value,0,N);
	for( i = 0;brdaddr_addr[i] != '\0';i++)
		p[5]->value[i] = brdaddr_addr[i];
	p[5]->value[i] = '\0';
	
	memset(p[6]->name,0,N);
	strcpy(p[6]->name , "\nHWADDR=");
	p[6]->name[8] = '\0';
	memset(p[6]->value,0,N);	
	for( i = 0;mac_addr[i] != '\0';i++)
		p[6]->value[i] = mac_addr[i];
	p[6]->value[i+1] = '\0';	

	
	p[0]->next = p[1];
	p[1]->next = p[2];p[2]->next = p[3];p[3]->next = p[4];p[4]->next = p[5];
	p[5]->next = p[6];p[6]->next = p[7];p[7]->next = p[8];p[8]->next = NULL;	
	
	//#ifdef DEBUG
	print(head);	
	//#endif
		
	save(filename,head);
	
	/*打印修改后的配置文件*/
	print(head);	
	
	return 0;
}

 从一个文件中读取数据，进行操作后，再写到另一个文件中：

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

#define LEN sizeof (struct gzb)

#define MAXLEN 20


struct gzb
{
 char name[MAXLEN];
 float gz,sanj,gs,sd;
 struct gzb *next;
};

float income_tax(float income,float insurance);


void main()
{
	FILE *fa,*fb;
	char buf[1024];
    struct gzb *p1;
    /**
	**  a.txt
	**  
	**  姓名   工资    三金
	**
    **/
	if((fb=fopen("b.txt","w+"))==NULL)
	{
	  printf("cannot open this file\n");
	  exit(1);
	}

    fprintf(fb,"姓名      工资     三金      税金       所得工资\n"); 
	
	if((fa=fopen("a.txt","r"))==NULL)
	{
		 printf("cannot open this a file\n");
		 exit(1);
	}
 

	while(fgets(buf,1024,fa)!=NULL)//此处可以做些技术性出来，是程序根据灵活性
	{

	  p1=(struct gzb*)malloc(sizeof(struct gzb));

	  sscanf(buf,"%s%f%f",p1->name,&p1->gz,&p1->sanj);
    
	  printf("%s %f %f\n",p1->name,p1->gz,p1->sanj);

	  p1->gs=income_tax(p1->gz,p1->sanj);

	  fprintf(fb,"%s %f %f %f %f\n",p1->name,p1->gz,p1->sanj,p1->gs,p1->gz - p1->sanj - income_tax(p1->gz,p1->sanj));

	 }
	 fclose(fa);
	 fclose(fb);
}

float income_tax(float income,float insurance)
{
	float taxincome,tax,rincome;  

	taxincome=income-insurance-3500;

	if(taxincome<=0)  

	  tax=0;  

	if(taxincome<=500)  

	  tax=taxincome*0.05;  

	if(taxincome>500 && taxincome<=2000)  

	  tax=taxincome*0.1-25;  

	if(taxincome>2000 && taxincome<=5000)  

	  tax=taxincome*0.15-125;  

	if(taxincome>5000 && taxincome<=20000)  

	  tax=taxincome*0.2-375;  

	if(taxincome>20000 && taxincome<=40000)  

	  tax=taxincome*0.25-1375;  

	if(taxincome>40000 && taxincome<=60000)  

	  tax=taxincome*0.3-3375;  

	if(taxincome>60000 && taxincome<=80000)  

	  tax=taxincome*0.35-6375;  

	if(taxincome>80000 && taxincome<=100000)  

	  tax=taxincome*0.4-10375;  

	if(taxincome>100000)  

	  tax=taxincome*0.45-1575;  

	if(tax <= 0)
	tax = 0;

	return(tax);

}