1a.c

liunx下的shell实现；进程、线程同步的实现；I/O系统调用的比较（mmap）——操作系统的课程设计

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#define N 1024
struct buffer
{
char buff[N];
struct buffer *next;
};
int main(void)
{
void shuchu(struct buffer *q,int j);
int fpin;
struct buffer *head=NULL,*p;
int i=1,j;
fpin=open("text",O_RDONLY);
if(fpin<0)
	{
	printf("can't open this file\n");
	return 1;
	}
printf("%d",fpin);
while(i)
{
p=(struct buffer*)malloc(sizeof(struct buffer));
if(head==NULL)
{p->next=NULL;head=p;}
else
{
p->next=head;
head=p;
}
j=i;
i=read(fpin,p->buff,N);
}
close(fpin);
shuchu(head,j);
} 
void shuchu(struct buffer *q,int j)
{
int fpout;
int i,flag=0;
char temp[N];
fpout=open("text",O_WRONLY);
do
{
for(i=N-1;i>=0;i--)
{
temp[N-i-1]=q->buff[i];
}
q=q->next;
if(flag==0)
		{
write(fpout,temp+1024-j,j);
		flag=1;
		}
else
		{
		write(fpout,temp,N);
		}
}while(q!=NULL);
close(fpout);
}