Linux man command number meaning 1 User Commands 2 System call3 C Library Functions 4 Devices and Special Files 5 File Formats and Conventions 6 Games et. al. 7 Miscellanea 8 System Administration tools and Deamons www.2cto.com 1. commands that can be operated by users in the shell environment, executable files 2, and functions and tools that can be called by the System kernel, the functions provided by the kernel. For example, open, write (through this, you can easily find out what header files need to be added when calling this function) 3. Some common functions and function libraries are mostly C function libraries, for example, printf, fread 4, device file description, usually File 5 under/dev, configuration file or some file formats such as passwd 6, left for the game, 7. Miscellaneous such as conventions and protocols defined by each game, Linux file system, network protocol, and ASCII code, such as man, environ 8, and system management commands, these commands can only be used by the system administrator, such as ifconfig 9. For kernel-related files, man 1 man: view the man command details.