Linux study Notes-network communication commands, system shutdown, shell application skills

Network Communication commands, system shutdown, shell application tips for Linux Study Notes 1. network communication commands www.2cto. com1. send a message to an individual. this person must write the online status user name. 2. send the message to the owner. you do not need to add the user name, as long as you log on to the linux system...
Network Communication commands, system shutdown, shell application tips for Linux Study Notes 1. network communication command www.2cto.com 1. send information to someone, this user must write the user name online. 2. send the information to everyone. if you do not need to add the user name, users logging on to the linux system will receive the wall 3 and ping commands, test whether the hosts on the network are connected. in command format, ping the IP address. observe the time and packet loss options during the test. if the network connection speed is low, check the network cable, when creating a network cable, the network cable will be extended due to the warmth of winter or summer. 4. ifconfig-a: View all network card information. ifconfig eth0: View eth0. ifconfig eth0: 192.168.0.23: modify the IP address of eth0, reboot will expire 2. reboot Command 1. shutdown-h now immediately shut down 2. reboot restarts the computer 3. shell application skills there are many shell types, you can run cat/etc/shells to check the installed shell [root @ CentOS-Test data] # cat/etc/shells/bin/sh/bin/bash/sbin/nologin/ bin/tcsh/bin/csh [root @ CentOS-Test data] # complete the command for bash Key, www.2cto.com to view the history command, that is, the used command: history use the up arrow key and down arrow key to find the previously executed command clear screen command: clear or press the shortcut key ctrl + l to delete the character before the cursor: ctrl + u to view the alias of the command: alias 4. the input/output redirection is the same as that of standard I/O, shell pre-defines three file descriptors (0, 1, 2) for each process, corresponding to: 0 :( STDIN) standard input 1 :( STDOUT) standard output 2 :( STDERR) standard error output redirection: enter a file separately:> [root @ CentOS-Test data] # ll/etc> tmp. msg:> [root @ CentOS-Test data] # ll/etc> tmp. msg input redirection: wall </etc/motd/lhc_xx.txt error redirection: cp-R/usr/backup/usr. bak 2>/bak. error 5. pipeline | function: you can output a command to another command, for example: 1. [root @ CentOS-Test/] # ll | more 2. [root @ CentOS-Test/] # ll/etc | grep init 3. [root @ CentOS-Test/] # ll/etc | grep init | wc-l: how many records are included in init? 4. wc-l/etc/services: how many lines are included in the services File? 6. how many lines are used in the command? connector 1, used; run [root @ CentOS-Test/] # pwd; ls; date in sequence to view the current path and then list the directories, finally, the system date 2 and the execution of commands before and after & are displayed in the logic and relationship, the command after it is run [root @ CentOS-Test/] # write Test