Linux系统编程

文末自带资料。

系统调用的文件操作：

#include <sys/types.h>
#include <unistd.h>
#include <sys/stat.h>
#include <stdio.h>
#include <fcntl.h>
#include <string.h>
#include <stdlib.h>
typedef struct student 
{
	int sno;
	char name[30];
	struct student *next ;
}student ;
student * createStu()
{
	student * head = NULL ;
	student *pnew = NULL ;
	char cmd ;
	while(1)
	{
		printf("添加学生么?  [y/n]\n") ;
		cmd = getchar() ;
		if('y' == cmd || 'Y' == cmd)
		{
			pnew = (student*)malloc(sizeof(student)) ;
			printf("sno = ") ;
			scanf("%d",&(pnew -> sno)) ;
			while(getchar()!='\n') ;
			printf("name = ") ;
			scanf("%s",pnew -> name) ;
			while(getchar()!='\n') ;
			pnew -> next = head ;
			head = pnew ;
		}else
			break ;
	}
	return head ;
}
void showStu(student*head)
{
	if(NULL == head)
	  printf("NONE data of student\n") ;
	student * p = head ;
	while(p)
	{
		printf("student : sno = %d , name = %s\n",p->sno,p->name) ; 
		p = p -> next ;
	}
}
student * freeStu(student *head)
{
	student * p = NULL ;
	while(head)
	{
		p = head ;
		head = head -> next ;
		free(p) ;
	}
	return head ;
}

int get_line(int fd , char *buf , int buf_max_len)
{
	if(NULL == buf)
	  return -1 ;
	int ret = 0;
	int ret2 ;
	char c ;
	while(1)
	{
		ret2 = read(fd, &c , 1) ;
		if(ret2 < 0)
		{
			perror("my read:\n") ;
			break ;
		}else if(ret2 == 0)
		{
			break ;
		}
		if('\n' == c || '\r' == c)
		  	break ;
		buf[ret] = c; 
		ret += ret2 ;
		if(ret >= buf_max_len)
		{
			printf("data over the container's max len") ;
			break ;
		}
	}
	return ret ;
}

int main(int argc , char **argv)
{
  	student *head =NULL ;
	/*head = createStu() ;
	showStu(head) ;
	int fw = open("./stu.txt",O_WRONLY|O_CREAT|O_TRUNC,0640) ;
	if(fw < 0)
	  	perror("creata stu.txt failed\n") ;
	else
	{
	  	student *temp = head ;
		char buf[sizeof(student)+1] = {0} ;
	  	while(temp)
		{
			sprintf(buf , "%d %s\n",temp->sno , temp -> name) ;
			if(write(fw , buf , strlen(buf)) != strlen(buf))
			{
				printf("write error %d %s\n",__LINE__ , __FILE__) ;
				break ;
			}
			temp = temp -> next ;
		}
	}
	close(fw) ;
	head = freeStu(head) ;
	if(NULL == head)
		printf("free finished!\n");*/
    printf("check file access\n") ;
	int acc = access(argv[1],W_OK|R_OK) ;
	if(acc == -1)
	{
		perror("access:") ;
	}else
	{
		printf("[%s] writable and readable\n",argv[1]) ;
	}

	printf("============read file ============\n") ;
	int fd = open("./stu.txt",O_RDONLY);
	if(fd < 0)
	{
		perror("my open: \n") ;
	}
	int ret ;
	char bufRe[1024] = {0};
	student *p = NULL ;
	while(1)
	{
		p = (student*)malloc(sizeof(student)) ;
		p -> next = NULL ;
		ret = get_line(fd, bufRe , sizeof(bufRe)) ;
		if(ret <= 0)
		  break ;
		sscanf(bufRe , "%d %s" , &(p->sno) ,p->name) ;
		p -> next = head ;
		head = p ;
	}
	showStu(head) ;
	close(fd) ;
	head = freeStu(head) ;
	if(NULL == head)
	  printf("free finished!\n") ;
	return 0 ;
}