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在Linux中man的使用频率应该是很高的，灵活运用它可以让自己快速的掌握一个不熟悉命令的使用方法。下面来介绍下man 环境CentOS6.8 man - format and display the on-line manual pages 在线使用手册格式及展示通俗点来说它就是命令的使用手册。它共分九个章节1、用户命令2、系统调用3、C库调用4、设备文件及特殊文件5、配置文件格式6、游戏7、杂项8、管理命令及守护进程9、Linux内核API（CentOS7以后出现）之所以分这九个章节是应为有的命令分属不同类，查看命令具体属于man中的哪个章节需要使用命令whatis COMMAND下面就命令echo为例来具体说明man的手册内容#whatis echoecho (1) - display a line of textecho (1p) - write arguments to standard outputecho [builtins] (1) - bash built-in commands, see bash(1)从上面可以看出来echo属于man的第一章节下面从具体的man 1 echo中解释具体每项的意义#man 1 echoNAME 命令名称及功能简要说明 echo - display a line of textSYNOPSIS 用法说明，包括可用的选项 echo [SHORT-OPTION]... [STRING]... echo LONG-OPTION :此符号内为必给内容 []:此符号内为可选内容 |：此符号表示多选一 {}：此符号表示为分组...:同一内容出现多次DESCRIPTION 命令功能的详尽说明，可能包括每一项的意义 Echo the STRING(s) to standard output. -n do not output the trailing newline -e enable interpretation of backslash escapes -E disable interpretation of backslash escapes (default) --help display this help and exit --version output version information and exit . . .AUTHOR 作者 Written by Brian Fox and Chet Ramey.REPORTING BUGS 报告程序bug的方式 Report echo bugs to [email protected] GNU coreutils home page: //www.gnu.org/software/coreutils/> General help using GNU software: //www.gnu.org/gethelp/> Report echo translation bugs to //translationproject.org/team/>COPYRIGHT 版权声明 Copyright 2010 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later //gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.SEE ALSO 另外参照 The full documentation for echo is maintained as a Texinfo manual. If the info and echo programs are properly installed at your site, the command info coreutils 'echo invocation' should give you access to the complete manual.有的命令中还有OPTIONS（说明每一个选项的意义）、FILES（此命令相关的配置文件）、ARGUMENTS（命令的作用对象），大致有上面这几项。 man命令中的快捷键，便于查看文本信息enter return键：向后翻一行 k：向前翻一行ctrl+d :向文件尾部翻半屏 ctrl+u:向文件首部翻半屏G:跳至最后一行 #G:跳转至指定行，#表示行号 man查找，用于在man手册中快速定位需要的信息/keyword:以keyword指定的字符串为关键字，从当前界面所在位置向文件尾部搜索；不区分字符大小写n:下一个 N:上一个？keyword:以keyword指定的字符串为关键字，从当前界面所在位置向文件首部搜索；不区分字符大小写n:跟收缩命令同方向，下一个 N:跟搜索命令反向，上一个 当不看man手册时q为退出 man的实际应用下面通过一个实际的问题，来说明man的作用例子：字符终端登陆时，显示当前登陆终端号，主机名和当前时间。要求使用man查找实现上述要求，提示:修改/etc/issue文件。怎么修改可以通过man查看issue求助。我们先用cat看下/etc/issue文件# cat /etc/issueCentOS release 6.8 (Final)Kernel on an m之后我们man issueFormatting page, please wait...ISSUE(5) Linux Programmer’s Manual ISSUE(5)NAME issue - pre-login message and identification fileDESCRIPTION The file /etc/issue is a text file which contains a message or system identification to be printed before the login prompt. It may contain various @char and char sequences, if supported by the getty-type pro- gram employed on the system.FILES /etc/issueSEE ALSO motd(5), agetty(8), mingetty(8)COLOPHON This page is part of release 3.22 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.Linux 1993-07-24 ISSUE(5)查看之后发现找不到一点有价值的信息，不过在最后提示我们可以查看motd、agetty、mingetty这三个文件。man motdMOTD(5) Linux Programmer’s Manual MOTD(5)NAME motd - message of the dayDESCRIPTION The contents of /etc/motd are displayed by login(1) after a successful login but just before it executes the login shell. The abbreviation "motd" stands for "message of the day", and this file has been traditionally used for exactly that (it requires much less disk space than mail to all users).FILES /etc/motdSEE ALSO login(1), issue(5)COLOPHON This page is part of release 3.22 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.Linux 1992-12-29 MOTD(5)motd里面也没有值得我们参考的信息，继续下一个man agenttyAGETTY(8) AGETTY(8)NAME agetty - alternative Linux gettySYNOPSIS agetty [-8ihLmnUw] [-f issue_file] [-l login_program] [-I init] [-t timeout] [-H login_host] port baud_rate,... [term] agetty [-8ihLmnw] [-f issue_file] [-l login_program] [-I init] [-t timeout] [-H login_host] baud_rate,... port [term]DESCRIPTION agetty opens a tty port, prompts for a login name and invokes the /bin/login command. It is normally invoked by init(8). agetty has several non-standard features that are useful for hard-wired and for dial-in lines: o Adapts the tty settings to parity bits and to erase, kill, end- of-line and uppercase characters when it reads a login name. The program can handle 7-bit characters with even, odd, none or space parity, and 8-bit characters with no parity. The following special characters are recognized: @ and Control-U (kill); #, DEL and back space (erase); carriage return and line feed (end of line). See also --erase-chars and --kill-chars options. o Optionally deduces the baud rate from the CONNECT messages pro- duced by Hayes(tm)-compatible modems. ... .. .由于这个手册内容很多，所以我们使用/issue快速找到关于/etc/issue的相关内容作为参考。 connection and turn on auto-answer after 1 ring.) /sbin/agetty -w -I ’ATE0Q1&D2&C1S0=1 ’ 115200 ttyS1ISSUE ESCAPES The issue-file (/etc/issue or the file set with the -f option) may con- tain certain escape codes to display the system name, date and time etc. All escape codes consist of a backslash () immediately followed by one of the letters explained below. b Insert the baudrate of the current line. d Insert the current date. s Insert the system name, the name of the operating system. l Insert the name of the current tty line. m Insert the architecture identifier of the machine, eg. i486 n Insert the nodename of the machine, also known as the hostname. o Insert the NIS domainname of the machine. O Insert the DNS domainname of the machine. r Insert the release number of the OS, eg. 1.1.9. t Insert the current time. u Insert the number of current users logged in. U Insert the string "1 user" or " users" where is the num- ber of current users logged in. v Insert the version of the OS, eg. the build-date etc. Example: On my system, the following /etc/issue file: This is .o (s m ) displays as This is thingol.orcan.dk (Linux i386 1.1.9) 18:29:30这里我们找到l可以解决显示当前登陆终端号问题， 解决主机名问题， 解决时间显示问题。既然找到了，那我们尝试修改/etc/issue文件。#vi /etc/issueCentOS release 6.8 (Final)Kernel on an mltime iswq保存退出。logout显示如下 问题解决。man的使用需要大家在平时的使用中慢慢摸索这样才会越用越得心应手。希望大家看了又所帮助。
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