11.1 Network Overview
11.1.1 Network Connection and IP Address
The IP address must be specified in order for a computer to be connected to the network. This IP address is always used when communicating with other computers on the network. The Raspberry Pi system is also assigned an IP address when connected to the network.
Chapter 11 Network Management
Chapter’s Main Topics
Here, we will look at how to inquire the network information in the Raspberry Pi system and how to configure various setting item to connect to the network through a desired manner.
It includes descriptions on the following topics:
■ Network overview
■ Network setting information
■ Using hostname
■ Wired network connection
■ Wireless network connection
■ Setting static ip
■ Activation and stop of network
■ Bluetooth setting and connection
10.9.4 “uniq” Command
This command performs the function of removing adjacent redundant data when reading data from the input or exporting the data to the output.
[Command Format]
uniq [option] [input] [output]
[Command Overview]
■ This removes adjacent redundant row data from input or output.
■ User privilege — Normal user.
10.9.3 “sort” Command
This command sorts the data in the specified file according to certain rule and then exports them to standard output.
[Command Format]
sort [option] [directory/file]
[Command Overview]
■ This sorts the data in the specified file.
■ User privilege — Normal user.
10.9.2 “wc” Command
This command counts and returns the number of line, word, and byte in the specified file.
[Command Format]
wc [option] [directory/file]
[Command Overview]
■ This calculates and reports the number of line, word, and byte in the specified file.
■ User privilege — Normal user.
10.9 Commands Related to Data Manipulation
10.9.1 “awk” Command
The “awk” command reads the specified file, finds the line that has a value matching the specified pattern, and performs the specified operation if the pattern matches. Here, the operation means a field manipulation in a line or an arithmetic operation using a field value. The name “awk” comes from the names of three people who developed it, Aho, Weinberger, and Kernighan.
Awk is a programming language with features such as Shell programming, BC, and the C programming language. It works perfectly with BC, and field variables with names like Shell arguments $1, $2, and $3 can be used on each input line. It also has a printing and control operator similar to the C language.
10.8.3 | (pipe) Command
In Linux, there is a way to use the output from the execution of one command as input to another command, which is “|” (pipe) command. The word “pipe” here means that all incoming input to the pipe is not removed or sent elsewhere, but is passed to the exit as it is entered without loss of content.
Normally, when a command is executed, it receives input data from an explicitly specified file or input device, processes it in the manner specified by the command, and sends the result to the output.
10.8.2 Redirection Command – Change Input and Output Device
In Linux, when you run a particular command, it sends its execution results to a predefined output device. However, if necessary, the execution result can be sent to an output device other than the predefined output device.
It is “<" and ">” (redirection) that is used in this case. If you use this command, it sends the execution result to the output device specified after this command. “redirect” means to change the default input device and the default output device where are set as the keyboard and monitor to another device.
Note that there are several commands as follows for user to redirect input and output with:
■ < and << -- Sends the processing result of the right to the left. ■ > and >> — Sends the processing result of the left to the right.
■ < and > — Overwrite existing file if one exists
■ << and >> — Append existing file if one exists
10.8 Commands to Adjust Input and Output
10.8.1 “xargs” Command
This command allows you to use the output of the previously executed command as an argument input to the next command.
[Command Format]
xargs [option] exec-command
10.7.4 “exit” Command – Terminate Process
The “exit” command is used to terminate process while a process is in progress.
[Command Format]
exit [exit-status]
[Command Overview]
■ This terminates the running process and set the exit status to the specified value.
■ User privilege — Normal user.