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In Linux, data is a file in data format; when the program is running, it will read files in certain specific formats. These files in specific formats are also data files "data files". You can use the last command to read it out, but when using cat, garbled characters will be read out.
#The operating environment of this tutorial: linux7.3 system, Dell G3 computer.
Data format file(data): Some programs will read files in certain formats during operation. Those Files in a specific format may be called data files. For example, when a user logs in, Linux will record the login data in the /var/log/wtmp file. This file is a data file that can be read out through the last command. But when using cat, garbled characters will be read. Because it is a file in a special format.
Extended knowledge
Ordinary file (regular file): It is a file for general access. Among the attributes displayed by ls -al, the first attribute is [-], for example [- rwxrwxrwx]. In addition, according to the content of the file, it can be roughly divided into:
1, Plain text file (ASCII): This is the most common file type in the Unix system, so it is called Plain text files are data whose content can be read directly, such as numbers, letters, etc. Almost all settings files belong to this file type. For example, use the command "cat ~/. rc" to see the contents of the file (cat reads the contents of the file).
2, Binary file (binary): The system actually only recognizes and can execute binary files (binary files). Executable files in Linux (scripts, text batch files are not counted) are in this format. For example, the command cat is a binary file.
3. Files in data format (data): Some programs will read files in certain formats during operation. Those files in specific formats can be called data files. For example, when a user logs in, Linux will record the login data in the /var/log/wtmp file. This file is a data file that can be read out through the last command. But when using cat, garbled characters will be read. Because it is a file in a special format.
Directory file (directory): It is a directory, the first attribute is [d], such as [drwxrwxrwx].
Connection file (link): similar to the shortcut under Windows. The first attribute is [l], for example [lrwxrwxrwx].
Device and device files (device): Some files related to system peripherals and storage are usually concentrated in the /dev directory. Usually divided into two types:
Block device file: It is an interface device that stores data for system access. Simply put, it is a hard disk. For example, the code of hard disk No. 1 is /dev/hda1 and other files. The first attribute is [b].
Character device file: the interface device of the serial port, such as keyboard, mouse, etc. The first attribute is [c].
Sockets: This type of file is usually used in network data connections. A program can be started to listen for client requests, and the client can communicate data through the socket. The first attribute is [s], which is the file type most commonly seen in the /var/run directory.
Pipe (FIFO, pipe): FIFO is also a special file type. Its main purpose is to solve errors caused by multiple programs accessing a file at the same time. FIFO is the abbreviation of first-in-first-out. The first attribute is [p].
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