内容来源于人民邮电出版社《Linux命令应用大词典》
讲述729个命令，1935个例子
学习Linux系统的参考书、案头书，遇到不懂的命令或命令选项一查即可
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本文出自 “airfish2000” 博客，更多命令查看博客：
http://airfish2000.blog.51cto.com/10829608/1881635
man命令
使用man命令可以格式化并显示在线的手册页。man会列出一份完整的说明，其内容包括命令语法、各选项的意义以及相关命令等。
命令语法：
man [选项] [名称]
命令中各选项的含义如表所示。
表 man命令选项含义
选项
含义
-M <路径>
指定man手册页的搜索路径
-a
显示所有的手册页，而不是只显示第一个
-d
主要用于检查，如果用户加入了一个新的文件，就可以用这个选项检查是否出错，这个选项并不会列出文件内容
-f
只显示出命令的功能而不显示详细的说明文件，和whatis命令一样功能
-p
字符串设定运行的预先处理程序的顺序
-w
不显示手册页内容，只显示将被格式化和显示的文件所在位置
例：显示pwd命令的man手册页。
[root@rhel~]# man pwd
PWD(1) User Commands PWD(1)
NAME
pwd - print name of current/workingdirectory
SYNOPSIS
pwd [OPTION]...
DESCRIPTION
Print the full filename of the currentworking directory.
-L, --logical
use PWD from environment, even ifit contains symlinks
-P, --physical
avoid all symlinks
--help display this help and exit
--version
output version information andexit
NOTE: your shell may have its own version of pwd, whichusually supersedes the version described here. Please
refer to your shell’s documentation fordetails about the options it supports.
AUTHOR
Written by Jim Meyering.
REPORTINGBUGS
Report pwd bugs to bug-coreutils@gnu.org
GNU coreutils home page:<http://www.gnu.org/software/coreutils/>
General help using GNU software:<http://www.gnu.org/gethelp/>
Report pwd translation bugs to<http://translationproject.org/team/>
COPYRIGHT
Copyright 2010 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later
<http://gnu.org/licenses/gpl.html>.
This is free software: you are free tochange and redistribute it. There is NOWARRANTY, to the extent permitted
by law.
SEEALSO
getcwd(3)
The full documentation for pwd ismaintained as a Texinfo manual. If theinfo and pwd programs are properly
installed at your site, the command
info coreutils 'pwd invocation'
should give you access to the completemanual.
GNUcoreutils 8.4 April2012 PWD(1)
//可以按[q]键退出man手册页
例：查看/etc/passwd文件的man手册页。
[root@rhel ~]# man 5 passwd
PASSWD(5) Linux Programmer’s Manual PASSWD(5)
NAME
passwd -password file
DESCRIPTION
Passwd is a text file, that contains a list of thesystem’s accounts, giving for each account some useful infor-
mation likeuser ID, group ID, home directory, shell, etc. Often, it also contains the encrypted passwords for
eachaccount. It should have general readpermission (many utilities, like ls(1) use it to map user IDs to user-
names), butwrite access only for the superuser.
In the goodold days there was no great problem with this general read permission. Everybody could read the
encrypted passwords, but the hardware was too slow to crack a well-chosen password, andmoreover, the basic
assumptionused to be that of a friendly user-community. These days many people run some version of the shadow
password suite, where /etc/passwd has "x" instead of encrypted passwords, and the encrypted passwordsare in
/etc/shadowwhich is readable by the superuser only.
If theencrypted password, whether in /etc/passwd or in /etc/shadow, is an emptystring, login is allowed without
even asking for a password. Note that this functionality may beintentionally disabled in applications, or con-
figurable (forexample using the "nullok" or "nonull" arguments topam_unix.so).
........................（省略）
例：显示passwd命令和/etc/passwd文件手册页所在位置。
[root@rhel ~]# man -w passwd
/usr/share/man/man1/passwd.1.gz
[root@rhel ~]# man -w5 passwd
/usr/share/man/man5/passwd.5.gz
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