rp2.c

linux 下模拟shell的实现。 支持管道等功能。读proc文件

/*This program realize the function that recive a filename from standard input device,
 * read the file and output the content by standard output device.
 * 
 * you must compeletly realize by systemcall ,and can't use libery function and parameters by main!
 *
 * Kong Xiangzhen 
 * class 33
 * 03055078
 * OCT 27th ,2006.
*/ 
#include <unistd.h>
#include <stdio.h>
#include <sys/types.h>
#include <fcntl.h>
#include <sys/stat.h>
#define max_read_size 2000
#define max_filename 100
int main()
{
	int fd,i_r,i_w;
	char buff[max_read_size];
	char tip[100]="Give the file's name that you want to read:";
	char readfilename[max_filename];
        
	if((i_w=write(1,tip,100))<0)
	{
		perror("write tip error!");
		exit(0);
	}
	if((i_r=read(0,readfilename,sizeof(readfilename)))<0)
	{
		perror("read filename error!");
		exit(0);
	}
	readfilename[i_r-1]='\0';
	if((fd=open(readfilename,O_RDONLY,0644))<0)
	{
		perror("open error!");
		exit(0);
	}

	if((i_r=read(fd,buff,sizeof(buff)))<0)
	{
		perror("read error!");
		exit(0);
	}
	if((i_w=write(1,buff,i_r))<0)
	{
		perror("write error!");
		exit(0);
	}
	return 0;
}