查看帮助

man

[!quote]
man - an interface to the on-line reference manuals

示例：

man ls
man 2 ls

通过 man man 查看如何使用man来获取帮助。

按功能、用途 对命令进行了划分，使用 page 参数查看指定分类下的命令。
page 及其 section 含义：

      The table below shows the section numbers of the manual followed by the types of  pages  they
       contain.

       1   Executable programs or shell commands
       2   System calls (functions provided by the kernel)
       3   Library calls (functions within program libraries)
       4   Special files (usually found in /dev)
       5   File formats and conventions eg /etc/passwd
       6   Games
       7   Miscellaneous (including macro packages and conventions), e.g. man(7), groff(7)
       8   System administration commands (usually only for root)
       9   Kernel routines [Non standard]

如果没有提供page 参数，那么显示按预设的section顺序找到的首个该命令的帮助。如 man open 显示 page 1 下的openvt 帮助。如果要查看系统调用function open，需要显式指定 section，man 2 open

page	command	name
1	open	openvt - start a program on a new virtual terminal (VT).
2	open	open, openat, creat - open and possibly create a file