shell学习day2

环境准备：

在虚拟机上安装Linux系统，遇到了一个问题-忘记root用户的密码了，解决方式是：1、在系统启动前输入esc,作用是让系统出现选择内核选项的界面；2、按e进入维护模式选择内核选项；3、再按“e”键，进入到编辑，在后面输入1，按回车退出；4、再按“b”键，进入到单用户模式下；5、进入到单用户模式后，输入密码设置指令：passwd root，按提示输入指令，修改后重启即可

实验开始：

使用 read 命令从 stdin 获取输入并赋值给 PERSON 变量，最后在 stdout 上输出：

代码：
#!/bin/bash
# Author : zhoudj
# Copyright zhoudj_20170430
# Script follows here:
echo "What is your name?"
read PERSON
echo "Hello, $PERSON"
运行脚本：
chmod +x ./first_shell.sh
$./first_shell.sh
What is your name?
zhoudj
Hello, zhoudj
$

注意，一定要写成./test.sh，而不是test.sh。运行其它二进制的程序也一样，直接写test.sh，linux系统会去PATH里寻找有没有叫test.sh的，而只有/bin, /sbin, /usr/bin，/usr/sbin等在PATH里，你的当前目录通常不在PATH里，所以写成test.sh是会找不到命令的，要用./test.sh告诉系统说，就在当前目录找

[oracle@localhost Desktop]$ su root
Password: 
[root@localhost Desktop]# cd /
[root@localhost /]# ls
bin   dev  home  lib64       media  opt   root  selinux  sys  usr
boot  etc  lib   lost+found  mnt    proc  sbin  srv      tmp  var
[root@localhost /]# mkdir study
[root@localhost /]# ls
bin   dev  home  lib64       media  opt   root  selinux  study  tmp  var
boot  etc  lib   lost+found  mnt    proc  sbin  srv      sys    usr
[root@localhost /]# rm -f study
rm: cannot remove `study': Is a directory
[root@localhost /]# rm -rf study
[root@localhost /]# ls
bin   dev  home  lib64       media  opt   root  selinux  sys  usr
boot  etc  lib   lost+found  mnt    proc  sbin  srv      tmp  var
[root@localhost /]# useradd zhoudj
[root@localhost /]# passwd zhoudj
Changing password for user zhoudj.
New password: 
BAD PASSWORD: it is based on a dictionary word
BAD PASSWORD: is too simple
Retype new password: 
Sorry, passwords do not match.
New password: 
BAD PASSWORD: it is based on a dictionary word
BAD PASSWORD: is too simple
Retype new password: 
passwd: all authentication tokens updated successfully.
[zhoudj@localhost study]$ udj
[zhoudj@localhost study]$ ls
first_shell
[zhoudj@localhost study]$ mv first_shell firsh_shell.sh
[zhoudj@localhost study]$ ls
firsh_shell.sh
[zhoudj@localhost study]$ more first_shell.sh
first_shell.sh: No such file or directory
[zhoudj@localhost study]$ vi
[zhoudj@localhost study]$ vi first_shell
[zhoudj@localhost study]$ vi first_shell.sh
[zhoudj@localhost study]$ first_shell.sh
bash: first_shell.sh: command not found
[zhoudj@localhost study]$ ./first_shell.sh
bash: ./first_shell.sh: Permission denied
[zhoudj@localhost study]$ chmod +x ./first_shell.sh
[zhoudj@localhost study]$ ./first_shell.sh
hello word
[zhoudj@localhost study]$ vi first_shell.sh
[zhoudj@localhost study]$ chmod +x ./first_shell.sh
[zhoudj@localhost study]$ $./first_shell.sh
bash: $./first_shell.sh: No such file or directory
[zhoudj@localhost study]$ $. /first_shell.sh
bash: $.: command not found
[zhoudj@localhost study]$ vi first_shell.sh
[zhoudj@localhost study]$ ./first_shell.sh
what is your name
p
hello,p:
[zhoudj@localhost study]$