man 手册

man --version# 查看版本
man 2 socket# 查看section2中的socket
yum install man-pages# 更新man手册man -f socket# 列出所有章节的socket
# man -f刚开始使用的时候不显示
# centos7执行mandb命令,7以下的版本执行makewhatis命令
# 之后执行man -f就生效了
[root@kafka100 cpp]# man -f socket
Socket (3pm)         - networking constants and support functions
socket (2)           - create an endpoint for communication
socket (3p)          - create an endpoint for communication
socket (7)           - Linux socket interface
# Vim中很多命令在man手册中也可以用
(空格向下翻页,b向上翻页,回车向下滚动一行,k向上滚动一行)
查找关键字用法和Vim中也一样
man man# man还可以查自己
man 7 inode

info文档

GNU项目以Info格式分发它的手册,使用info阅读器进行阅读
# The GNU Project distributes most of its manuals in the Info format, which you read using an Info reader.# You are talking to the program Info, for reading documentation
# There are two ways to use Info:from within Emacs or as a stand-alone reader that you can invoke from a shell using the command info
# There are two primary Info readers:
一个是独立程序(也就是info命令),是Texinfo发行版的一部分,只用来读info files
# info,a stand-alone program designed just to read Info files
# The Info program is part of the Texinfo distribution
# Info files are typically the result of processing Texinfo files with the program makeinfo(also in the Texinfo distribution)
# Type info at your shell's command line.This approach uses a stand-alone program designed just to read Info files.
另一个是Emacs中的info包
# the info package in GNU Emacs, a general-purpose editor.
# Type emacs at the command line;then type C-h i (Control-h, followed by i).This approach uses the Info mode of the Emacs editor.man info# Read documentation in Info format.
info --version
info info
info -h
info info -w# print physical location of Info file.
info ls -w
ls /usr/share/infoFile是当前文档信息来源的文件名
UP是上级节点
PREV是同一级的上个节点
Next是同一级的下个节点进入到info文档中后
<h>:查看帮助命令
<q>:退出info文档
<space>:向下翻页
<del>:向上翻页
<home>:Go to the beginning of this node.
<end>:Go to the end of this node.

Info files are created from '.texinfo' source, which is a special kind of markup language.
The program used to convert '.texinfo' files to '.info' files is GNU TexInfo.The files are usually stored in /usr/share/info but are viewed with a dedicated program, such as the info command.
The /usr/share/info/dir file is used when info is run with no parameters. 

man displays manpages, typically stored in /usr/share/man, while info displays Info documents, typically stored in /usr/share/info
Additionally, Info documents are normally available in a tree structure, rooted in /usr/share/info/dir
Type info and you will get given an index of all the info files.That index is stored in /usr/share/info/dir
GNU软件包的手册
info程序
info文档
https://www.learnlinux.org.za/courses/build/shell-scripting/ch01s02.html
https://unix.stackexchange.com/questions/582288/does-the-info-command-display-man-pages