--help: 是一个工具选项,可以用来显示一些工具的信息
man : 可以显示系统手册页中的内容，这些内容大多数都是对命令的解释信息
PS: () Space 键可以显示下一屏的文本信息
() q 键是退出
info: 是一个基于菜单的超文本系统，是由GNU项目开发并由Linux发布。
info 工具包括一些关于Linux Shell,工具，GNU项目开发程序说明文档
PS: () ? 键可以列出info窗口中的相关命令
() Space 键可以进行滚动浏览
info
File: dir Node: Top This is the top of the INFO tree This (the Directory node) gives a menu of major topics.
Typing "q" exits, "?" lists all Info commands, "d" returns here,
"h" gives a primer for first-timers,
"mEmacs<Return>" visits the Emacs topic, etc. In Emacs, you can click mouse button on a menu item or cross reference
to select it. * Menu: Archiving
* Cpio: (cpio). Copy-in-copy-out archiver to tape or disk.
* Tar: (tar). Making tape (or disk) archives. Basics
* Common options: (coreutils)Common options.
Common options.
* Coreutils: (coreutils). Core GNU (file, text, shell) utilities.
* Date input formats: (coreutils)Date input formats.
* File permissions: (coreutils)File permissions.
Access modes.
* Finding files: (find). Operating on files matching certain criteria.
* ed: (ed). The GNU Line Editor. Editors
* nano: (nano). Small and friendly text editor. Emacs
* IDN Library: (libidn)Emacs API.
-----Info: (dir)Top, lines --Top-----------------------------------------------------------------
Welcome to Info version 4.13. Type h for help, m for menu item.
help
[root@dep5 ~]# help
GNU bash, version 4.1.()-release (x86_64-redhat-linux-gnu)
These shell commands are defined internally. Type `help' to see this list.
Type `help name' to find out more about the function `name'.
Use `info bash' to find out more about the shell in general.
Use `man -k' or `info' to find out more about commands not in this list. A star (*) next to a name means that the command is disabled. job_spec [&] history [-c] [-d offset] [n] or history -anrw [>
(( expression )) if COMMANDS; then COMMANDS; [ elif COMMANDS; th>
. filename [arguments] jobs [-lnprs] [jobspec ...] or jobs -x command >
: kill [-s sigspec | -n signum | -sigspec] pid | >
[ arg... ] let arg [arg ...]
[[ expression ]] local [option] name[=value] ...
alias [-p] [name[=value] ... ] logout [n]
bg [job_spec ...] mapfile [-n count] [-O origin] [-s count] [-t] >
bind [-lpvsPVS] [-m keymap] [-f filename] [-q na> popd [-n] [+N | -N]
break [n] printf [-v var] format [arguments]
builtin [shell-builtin [arg ...]] pushd [-n] [+N | -N | dir]
caller [expr] pwd [-LP]
case WORD in [PATTERN [| PATTERN]...) COMMANDS ;> read [-ers] [-a array] [-d delim] [-i text] [-n>
cd [-L|-P] [dir] readarray [-n count] [-O origin] [-s count] [-t>
command [-pVv] command [arg ...] readonly [-af] [name[=value] ...] or readonly ->
compgen [-abcdefgjksuv] [-o option] [-A action]> return [n]
complete [-abcdefgjksuv] [-pr] [-DE] [-o option]> select NAME [in WORDS ... ;] do COMMANDS; done
compopt [-o|+o option] [-DE] [name ...] set [--abefhkmnptuvxBCHP] [-o option-name] [arg>
continue [n] shift [n]
coproc [NAME] command [redirections] shopt [-pqsu] [-o] [optname ...]
declare [-aAfFilrtux] [-p] [name[=value] ...] source filename [arguments]
dirs [-clpv] [+N] [-N] suspend [-f]
disown [-h] [-ar] [jobspec ...] test [expr]
echo [-neE] [arg ...] time [-p] pipeline
man太多了= =