type 判断内部外部命令
内置命令bash自带的：help
外部命令有路径的
usr/share/man/man
man配置的使用技巧
先看man的章节
命令手册章节
1，用户命令
2，系统调用，system call
3，库调用，library call
4，设备文件
5，配置文件
6，游戏
7，杂项
8，管理命令
使用whatis匹配关键字，根据关键字选择，章节，
man精确匹配命令
whatis+命令：显示指定关键字存在帮助手册的章节相关信息和简单说明
[root@localhost ~]# whatis passwd
passwd (1) - update user's authentication tokens
passwd (5) - password file
passwd [sslpasswd] (1ssl) - compute password hashes
[root@localhost ~]#
模糊匹配
模糊匹配方式显示指定的关键字的描述信息中存在帮助手册相关信息
[root@localhost ~]# man -k passwd
chpasswd (8) - update passwords in batch mode
fgetpwent_r [getpwent_r] (3) - get passwd file entry reentrantly
getpwent_r (3) - get passwd file entry reentrantly
gpasswd (1) - administer /etc/group and /etc/gshadow
htpasswd (1) - Manage user files for basic authentication
lpasswd (1) - Change group or user password
lppasswd (1) - add, change, or delete digest passwords
pam_localuser (8) - require users to be listed in /etc/passwd
pam_passwdqc (8) - Password quality-control PAM module
passwd (1) - update user's authentication tokens
passwd2des [xcrypt] (3) - RFS password encryption
passwd (5) - password file
passwd [sslpasswd] (1ssl) - compute password hashes
saslpasswd2 (8) - set a user's sasl password
smbpasswd (5) - The Samba encrypted password file
smbpasswd (8) - change a users SMB password
userpasswd (1) - A graphical tool to allow users to change their passwords
[root@localhost ~]#
man命令借助less命令查看文件内容法则
还有几个命令：
info：获取在线文档
changelog：更新日志
install:安装说明
README：程序说明信息
www.redhat.com/docs 官方文档
