RHEL6 basics 5 x-basic operations and internal and external commands on windows

I. shell and command prompt

In Linux, GNOME and KDE are the software that provides the X Window Function. GNOME is used by default in RHEL6.

The character interface of Linux is called Shell. There are many software responsible for providing Shell functions, such as B shell, c shell, t shell, k shell, and sh. The default Shell used in RHEL6 is Bash. Shell can be divided into two modes: Interactive Mode waiting for your input) and non-interactive mode script form ).

Shell character interface entry method:

1. X-window virtual character Terminal

Right-click the X-window Interface-open E in the terminal )]

650) this. width = 650; "src =" http://www.bkjia.com/uploads/allimg/131228/001211I12-0.png "style =" float: none; "title =" 1.png" alt = "111826274.png"/>

650) this. width = 650; "src =" http://www.bkjia.com/uploads/allimg/131228/0012112295-1.png "style =" float: none; "title =" 2.png" alt = "111827932.png"/> [justin @ localhost desktop] $ <=> [user name @ current host name location] user type $: normal user ;#: administrator user)

2. links through tools such as putty, xshell, and SecureCRT
You need to know the machine IP address through the tool link:
Right-click the computer icon in the upper-right corner of the desktop and select system eth0 to link to internet. Right-click the computer icon and choose edit link. --- Select system eth0 --- edit --- Select automatic link ], in this way, the NIC will be restarted automatically, and then the IP address is 10.15.72.194 on the terminal.

650) this. width = 650; "src =" http://www.bkjia.com/uploads/allimg/131228/001211L57-2.png "style =" width: 750px; height: 209px; "title =" 1.png" width = "750" height = "209" border = "0" hspace = "0" vspace = "0" alt = "132156696.png"/>

650) this. width = 650; "src =" http://www.bkjia.com/uploads/allimg/131228/001211D34-3.png "style =" float: none; "title =" 2.png" alt = "132156527.png"/>
Here, xshell is used. Enter the ssh ip address in the tool. Then, click Accept & save and enter the user name and password.
650) this. width = 650; "src =" http://www.bkjia.com/uploads/allimg/131228/00121111H-4.png "title =" 1.png" alt = "132720460.png"/>

Internal commands: refers to the commands integrated in Shell, which are part of the shell. The system does not have a program file that corresponds to the command separately. As long as the shell is executed, internal commands are automatically loaded into the memory, which can be directly used by users. Such as cd commands. External commands: Considering the running efficiency and other reasons, it is impossible to integrate all the commands into the shell. More Linux commands are independent from the shell, which are called external commands. Each external command corresponds to a file in the system, and the Linux system must know the location of the program file corresponding to the external command before the shell can load and execute these commands. For example, cp and ls all belong to external commands. Note: Most program files of External commands are stored in/bin,/sbin,/usr/bin ...... In these directories, the Linux system will add these paths to a variable named PATH by default, run the "echo $ PATH" command to display the ":" interval between the directory paths saved in the PATH variable ).
[Root @ localhost ~] # Echo $ PATH
/Usr/lib64/qt-3.3/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin: /root/bin
Every time you want to execute an external command, the Linux system will first find the program file corresponding to the command from the paths saved by the PATH variable, only when the program file is found can external commands be correctly executed. This means that if the program file corresponding to an external command is deleted, or the directory where the external command program file is stored is not added to the PATH variable, the external command cannot be executed normally.

This article is from the justin blog, please be sure to keep this source http://justinpeng.blog.51cto.com/7662323/1300059