北邮linux大作业2016参考答案

1.(1)date //打印系统当前的日期和时间等信息结果：2017年 01月 09日星期一 19:09:15 CST(2)arch 显示机器的处理器架构(1)uname -m 显示机器的处理器架构(2)uname -r 显示正在使用的内核版本(3) 没测试广播！DELAY=1200wall 'The System is going REBOOT for halt in 20 minutes. Please SAVE your work. \r'for i in $(seq $DELAY | tac);doecho -en "The System is going REBOOT for halt in \033[31m ${i} \033[37m seconds. Please SAVE your work. \r"sleep 1done/sbin/reboot -h 02.(1)操作步骤：（1）终端窗口下执行命令crontab –e，使用vim编辑计划任务；（2）在vim窗口中，添加如下几项：(1) 10 2 * * * rm -r /cdf(2) 0 0 * * 7 cp -f -r /user/backup /tmp/ #由于是备份，采用强制复制模式3.#! bin/shsign=1#输入if[ "$#" != 2 ]thenecho "please make sure that you enter 2 arguments, first is the source file, second is the destination directory."exit 1fi #if 1 , check the amount of the arguments.# 3.检查源文件是否存在if[ ! -f "$1" ]thenecho "the source file(the first argument) doesn't exist, please check your arguments" exit 1fi #if 2 , check if the source file exists.# 1.检查源文件和目标文件是否是同一个文件if[ "$1" = "$2" ]thenecho "the source file and the destination is the same file!"exit 1fi #if 3 , check the amount of the arguments.# 2.检查目标文件名格式是否正确ifecho "$2" | grep -q '^[a-zA-Z0-9_/.]\+$'thencontinueelseecho "your destination is a invalid file name."exit 1fi #if 4, check if the destination is a invalid file name# 4.检查目标文件是否存在，如果目标文件已经存在则询问是否覆盖if[ -f "$2" ]thenwhile [ $sign -eq 1 ]doecho "the destination file has been created, are u sure to overwrite it?(please enter y/n)" read YesOrNocase "$YesOrNo" iny)cp $1 $2echo "------------------------------------------"echo "the file has been copied"sign=0continue;;Y)cp $1 $2echo "------------------------------------------"echo "the file has been copied"sign=0continue;;n)sign=0break;;N)sign=0break;;*)sign=1continue;;esacdoneexit 1fi #if 5, make sure if the user wanna overwrite the file that has been created.cp $1 $2if [ "$?"=0 ]thenecho "copy successfully."elseecho "some error(s) occured."fi #if 6, to check if there's sth wrong.4.ssh 的非交互式登陆环境说明：工作服务器 A： IP 地址 10.193.251.191，操作系统 RHEL5.5，已建立用户 root工作服务器 B： IP 地址 10.193.251.192，操作系统 RHEL5.5，已建立用户 liubo思路：在服务器 A 生成一对 RSA 密钥，自己保留私钥。

将公钥附加到登陆服务器 B 的authorized_keys 中， A 登陆 B，就不用交互式输入密码了。

>>在服务器 A 上生成一对密钥（以 root 的身份执行）[root@img181 ~]# ssh-keygen -t rsaGenerating public/private rsa key pair.Enter file in which to save the key (/root/.ssh/id_rsa):Enter passphrase (empty for no passphrase):Enter same passphrase again:Your identification has been saved in /root/.ssh/id_rsa.Your public key has been saved in /root/.ssh/id_rsa.pub.The key fingerprint is:1b:59:a1:1c:10:f4:8c:a9:b2:59:e2:25:80:7e:e8:ae root@img181>>登陆到工作服务器 B 上创建.ssh 目录（以用户 liubo 为例）。

[liubo@img172 ~]$ mkdir .ssh[liubo@img172 ~]$ chmod 700 .ssh>>在 A 服务器上执行远程拷贝公钥到 B 服务器：[root@img181 ~]# scp .ssh/id_rsa.publiubo@10.193.251.172:/home/liubo/.ssh/authorized_keys这样， 181 服务器上用户 root 到 172 服务器上的用户 liubo 之间的无交互 ssh 登陆就完成了。

5.#! /bin/bash#文件读取，分别将第二、三列读入到两个数组index、rele中i=0for line in `cut -f2 -d" " data.txt`doindex[${i}]=$linelet i=${i}+1donej=0for line in `cut -f3 -d" " data.txt`dorele[${j}]=$linelet j=${j}+1done#检查文件与标签数是否相等if test ${#rele[@]]} -ne ${#index[@]]}echo "Fatal Error: The num of images and indicators are unequal!" exit 0finum=${#index[@]}#利用bc进行浮点数运算ck=0tmp=0for i in $(seq $num)doj=i-1ck=$(echo "scale=5; $ck + ${rele[${j}]}" | bc)tmp=$(echo "scale=5; $tmp + ${rele[${j}]} * $ck / $i" | bc)doneAP=$(echo "scale=5; $tmp / $ck" | bc)echo "The average precise is $AP."6./s/blog_6a3100f20102v2po.html7.Makefilemain:main.o function.og++ -o main main.o function.omain.o:main.cpp function.hg++ -c main.cppfunction.o:function.cpp function.hg++ -c function.cppclean:rm -rf *.o mainfunction.h#ifndef _FUNCTION_H#define _FUNCTION_Hlong add_2(long s1,long s2);long convert2Binary(long sum);long convert2Decimal(long str);function.cpp#include "function.h"#include <iostream>#include <sstream>#include <string>#include "stdlib.h"using namespace std;long convert2Decimal(long str){std::stringstream stream;string p;stream<<str;stream>>p;int i,num=0;for(i=0;p[i]!='\0';i++){if(p[i]=='1' || p[i]=='0'){num<<=1;num+=p[i]-'0';}else{cout<<"不是二进制数\n"<<endl; exit(0);}}return num;}long add_2(long s1,long s2){long sum;sum=s1+s2;return sum;}long convert2Binary(long num){std::stringstream stream;bool flag = 0;string q;int j=1;long result;for(int i = 32; i >= 0; i--){if(num & (1 << i)){ q[j]="1"; cout<<j<<endl;cout<<q[j]<<endl;flag=1;j++;}else{ if(flag==1)q[j]=0;j++;//cout<<q[j]<<endl;}}cout<<q;stream<<q;stream>>result;cout<<result;return result;}8.一：服务器端的设定（以 LINUX 为例）服务器端的设定都是在/etc/exports 这个文件中进行设定的，设定格式如下：欲分享出去的目录 IP1(参数 1，参数 2） IP2（参数 3，参数 4）上面这个格式表示，同一个目录分享给两个不同的主机，但提供给这两台主机的权限和参数是不同的，所以分别设定两个主机得到的权限。