http://blog.csdn.net/hello_hwc
我的虚拟机系统是CentOS,版本较老,谅解
一、为什么要学习帮助命令?授人以鱼不如授人以渔,学会了怎么看帮助文档,是寻找到一个解决一类问题,而不是一个问题的方法。
二、常用的几个命名
1、man
-w 打印相关帮助文档的位置
-k 在man页中查找指定字符串和apropos命令相同
-f 和whatis相同
然后我们通过man ls命令来详细分析下man page中的内容
- [root@localhost ~]# man ls
- LS(1) User Commands LS(1)
- NAME
- ls - list directory contents
- SYNOPSIS
- ls [OPTION]... [FILE]...
- DESCRIPTION
- List information about the FILEs (the current directory by
- default). Sort entries alphabetically if none of -cftuvSUX
- nor --sort.
- Mandatory arguments to long options are mandatory for short
- options too.
- -a, --all
- do not ignore entries starting with .
- -A, --almost-all
- do not list implied . and ..
- ...中间省略
- AUTHOR
- Written by Richard Stallman and David MacKenzie.
- REPORTING BUGS
- Report bugs to <bug-coreutils@gnu.org>.
- COPYRIGHT
- Copyright © 2006 Free Software Foundation, Inc.
- This is free software. You may redistribute copies of it
- under the terms of the GNU General Public License
- <http://www.gnu.org/licenses/gpl.html>. There is NO WAR-
- RANTY, to the extent permitted by law.
- SEE ALSO
- The full documentation for ls is maintained as a Texinfo man-
- ual. If the info and ls programs are properly installed at
- your site, the command
- info ls
- should give you access to the complete manual.
- ls 5.97 February 2010 LS(1)
这里可以看到,info ls可以给出详细描述
- NAME 名字,简单的命令是用来做什么的
- SYNOPSIS 简短的指令使用语法
- DESCRIPTION 详细的描述命令的使用方法
- OPTIONS 针对SYNOPSIS,进行详细的阐述
- COMMANDS 执行的时候可下达的命令
- FILES 指令相关的文件
- SEE ALSO 和这个指令相关的命令
- EXAMPLE 范例
- BUGS 尚存在的漏洞
- COPYRIGHT 版权信息
- REPORTING BUGS 发现Bug可以上传的邮箱
- AUTHOR 作者
然后,又会看到LS(1)后面跟了一个1,这个数字也是有特定含义的
- 1 指令或者可执行文档
- 2 内核可调用的函数
- 3 常用函数库
- 4 档案说明
- 5 档案格式
- 6 游戏
- 7 linux系统的说明性内容
- 8 root可用的管理命名
- 9 和内核相关的文件
在man页中如何翻页,查找
箭头上下 上下行切换
Home/End 到第一页、最后一页
/String 查找一个字符串,n下一个查找到的结果,N上一个
q 结束这次
何时用man命令
我的心得是:这个命令基本不熟悉,需要详细的去看看自己想要的功能如何使用的时候,一般顺序是NAME-SYNOPSIS-DESCRIPTION-EXAMPLE
2、--help
列出常用命名的常用选项
使用场合:知道这个命令的使用领域,和简单使用方法,只是不熟悉某些选项
- [root@localhost ~]# file --help
- Usage: file [OPTION]... [FILE]...
- Determine file type of FILEs.
- -m, --magic-file LIST use LIST as a colon-separated list of magic
- number files
- -z, --uncompress try to look inside compressed files
- -b, --brief do not prepend filenames to output lines
- -c, --checking-printout print the parsed form of the magic file, use in
- conjunction with -m to debug a new magic file
- before installing it
- -f, --files-from FILE read the filenames to be examined from FILE
- -F, --separator string use string as separator instead of `:'
- -i, --mime output mime type strings
- -k, --keep-going don't stop at the first match
- -L, --dereference causes symlinks to be followed
- -n, --no-buffer do not buffer output
- -N, --no-pad do not pad output
- -p, --preserve-date preserve access times on files
- -r, --raw don't translate unprintable chars to \ooo
- -s, --special-files treat special (block/char devices) files as
- ordinary ones
- --help display this help and exit
- --version output version information and exit
3、whatis
查找whatis的数据库,寻找关键字的描述信息。在我们学会了man之后,可以直接man whatis来看信息
使用场合:我们想知道这个命令使用来干嘛的,或者我们想知道这个命令的种类
- [root@localhost ~]# whatis ls
- ls (1) - list directory contents
- ls (1p) - list directory contents
- [root@localhost ~]# whatis CD
- cd (1p) - change the working directory
- cd [builtins] (1) - bash built-in commands, see bash(1)
4、help
查看shell内建指令的帮助信息,例如我们cd就是一个bash内建指令
- [root@localhost ~]# cd --help
- bash: cd: --: invalid option
- cd: usage: cd [-L|-P] [dir]
- [root@localhost ~]# help cd
- cd: cd [-L|-P] [dir]
- Change the current directory to DIR. The variable $HOME is the
- default DIR. The variable CDPATH defines the search path for
- the directory containing DIR. Alternative directory names in CDPATH
- are separated by a colon (:). A null directory name is the same as
- the current directory, i.e. `.'. If DIR begins with a slash (/),
- then CDPATH is not used. If the directory is not found, and the
- shell option `cdable_vars' is set, then try the word as a variable
- name. If that variable has a value, then cd to the value of that
- variable. The -P option says to use the physical directory structure
- instead of following symbolic links; the -L option forces symbolic links
- to be followed.
其他的内建指令
- alias, bg, bind, break, builtin, cd, command,
- compgen, complete, continue, declare, dirs, disown, echo,
- enable, eval, exec, exit, export, fc, fg, getopts, hash, help,
- history, jobs, kill, let, local, logout, popd, printf, pushd,
- pwd, read, readonly, return, set, shift, shopt, source, sus-
- pend, test, times, trap, type, typeset, ulimit, umask, una-
- lias, unset, wait