1、寫入數字

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>

#define BUFFER_SIZE 1024
#define FILE_PATH "./file.txt"
/*
* 程式入口
 * */
int main(int argc,char **argv)
{
	int test_fd = -1;
	int ret = 1;
	int buffer = 500;
	int num = 0;


	/*開啟或建立原始檔，並將檔案長度截斷為0*/ 
	if((test_fd=open(FILE_PATH, O_RDWR|O_CREAT|O_TRUNC))==-1) 
	{ 
		printf("Open %s Error\n",FILE_PATH); 
		exit(1); 
	} 
	/*寫入一個數字*/
	ret = write(test_fd, &buffer, sizeof(int));
	if( ret < 0)
	{
		printf("write Error\n"); 
		exit(1); 
	}
	printf("write %d byte(s) data\n",ret);
	
	/*將檔案指標移到最開始處去讀檔案中寫入的數字*/
	lseek(test_fd, 0L, SEEK_SET);
	ret= read(test_fd, &num, sizeof(int));
	if(ret==-1)
	{
		printf("read Error\n"); 
		exit(1);		
	}		
	printf("read %d byte(s) data，the number is %d\n", ret, num);
	
	close(test_fd); 
	exit(0); 
}
	

 

2、寫入結構體

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

#define FILE_PATH "./file.txt"

typedef struct file_record
{
	int index;
	int file_size;
	time_t timep;
}FILE_RECORD;

int main()
{
    int ret = 0;
    int fd = -1;
	time_t   timep = 0;
	FILE_RECORD file_record;
	struct stat buf;
	
	memset(&file_record, 0, sizeof(FILE_RECORD));
	memset(&buf, 0, sizeof(struct stat));
	
    time(&timep); 
	stat(FILE_PATH, &buf);
	/*開啟或建立原始檔，並將檔案長度截斷為0*/ 
	if((fd=open(FILE_PATH, O_RDWR|O_CREAT|O_TRUNC))==-1) 
	{ 
		printf("Open %s Error\n",FILE_PATH); 
		exit(1); 
	}
	
	file_record.index = fd;
	file_record.file_size = buf.st_size;
	file_record.timep = timep;
	
	/*寫入一個結構體*/
	ret = write(fd, &file_record, sizeof(FILE_RECORD));
	if( ret < 0)
	{
		printf("write Error\n"); 
		exit(1); 
	}
	printf("write %d byte(s) data\n",ret);
	
	memset(&file_record, 0, sizeof(FILE_RECORD));
	
	/*將檔案指標移到最開始處去讀檔案中寫入的結構體*/
	lseek(fd, 0L, SEEK_SET);
	ret= read(fd, &file_record, sizeof(FILE_RECORD));
	if(ret==-1)
	{
		printf("read Error\n"); 
		exit(1);		
	}		
	printf("read %d byte(s) data，the time is %s\n", ret, ctime(&(file_record.timep)));
	
	close(fd); 
	exit(0); 
	
}