Spark修炼之道（基础篇）——Linux大数据开发基础：第二节：Linux文件系统、目录（一）

本节主要内容

1. 如何获取帮助文档
2. Linux文件系统简介
3. 目录操作
4. 访问权限

1. 如何获取帮助文档

在实际工作过程当中，经常会忘记命令的使用方式，例如ls命令后面可以跟哪些参数，此时可以使用man命令来查看其使用方式，例如

<code class="hljs mel has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//man命令获取命令帮助手册</span>xtwy<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:~$ man <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">ls</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

可以使用键盘上的 来显示下一行或上一行命令，也可以使用 进行上一页或下一页（屏）命令的查看，另外 空格鍵也可以用来显示下一屏的命令。想退出命令查看，直接按q鍵退出即可，也可以h鍵显示less命令列表（man命令通过less命令输出结果）

2. Linux文件系统简介

（一） 文件和目录

本节从使用者的角度来介绍Linux文件系统，Linux根据文件形式将文件分为目录和普通文件，如下图： 
 
目录或文件的名称长度不超过255个字符，文件或目录名可由下列字符构成：

• Uppercase letters (A–Z)
• Lowercase letters (a–z)
• Numbers (0–9)
• Underscore ( _ )
• Period(.)
• Comma(,） 
  文件或目录名区分大小写，属于不同的文件或目录

（二） 文件扩展名与不可见文件名

与Window操作系统有很大不同的是，Linux文件对文件扩展名没有强制要求，例如假设编写了一个c语言源文件，你可以将其命名为complier.c，也可以是其它如complier、complier.ccc等文件名，但不推荐这么做，因为如果能将文件扩展名与特定的文件进行关联的话，有利于理解文件内容，目前约定成俗的linux文件扩展名如下表：

带扩展名的文件名扩展名的含义max.cC语言源文件max.o编码后的目标代码文件maxmax.c对应的可执行文件memo.txt文本文件memo.pdfpdf文件，必须在GUI界面上使用xpdf或kpdf才能查看memo.psPostScript文件，必须在GUI界面上使用ghostscript或kpdf才能查看memo.z经压缩程序压缩后的文件，可使用uncompress或gunzip解压memo.gz经gzip压缩程序压缩后的文件，可使用gunzip解压memo.tar.gz或memo.tgz经gzip压缩后的tar归档文件,可使用gunzip解压memo.bz2经bzip2压缩后的文件,可使用bunzip2解压memo.htmlhtml文件，使用GUI环境的firefox查看memo.jpg等图像文件,使用GUI环境的照片查看器打开

在前一讲中我们看到，linux中还存在大量的隐藏文件，采用ls -a 命令可以显示，想定义隐藏文件，只要文件名或目录以.开始即可 

（三） 绝对路径与相对路径

在Linux中绝对路径与相对路径是一个很重要的概念，下图给出了什么是绝对路径 
 
所有以根目录”/”作为开始的都是绝对路径，其它的均为相对路径

<code class="hljs mel has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//绝对路径访问</span>xtwy<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:~/Public$ cd /home/xtwy<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:/home$ <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">ls</span>xtwy<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//相对路径访问</span>xtwy<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:/home$ cd xtwy/</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li></ul>

3. 目录操作

（一） 创建目录 mkdir

为演示方便，使用下列目录结构进行演示：

1 绝对路径创建方式

<code class="hljs mel has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//使用绝对路径创建</span>root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:/home# mkdir /home/<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">max</span>root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:/home# <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">ls</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">max</span>  xtwyroot<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:/home# </code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li></ul>

2 相对路径创建方式

<code class="hljs mel has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//使用相对路径进行创建</span>root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:/home# mkdir <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">max</span>/namesroot<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:/home# mkdir <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">max</span>/temproot<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:/home# mkdir <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">max</span>/literatureroot<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:/home# cd <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">max</span>root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:/home/<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">max</span># mkdir demoroot<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:/home/<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">max</span># <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">ls</span>demo  literature  names  temp</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li></ul>

有时不想层层目录创建，此时可以在mkdir 后面加上参数 -p（parents），将父子目录一起创建

<code class="hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:/home/max</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># mkdir -p literature/promo</span>root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:/home/max</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># ls</span>demo  literature  names  temproot<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:/home/max</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># cd literature/</span>root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:/home/max/literature</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># ls</span>promo</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li></ul>

（二） 更改目录 cd

工作目录与主目录的区别 
用户每次登录后的默认目录就是主目录，与系统会话期间保持不变，主目录用~表示

<code class="hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">xtwy<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:/root</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$ </span>cd ~xtwy<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:~</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$ </span>pwd/home/xtwy</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

工作目录又称当前目录，cd命令执行完成后的目录就是工作目录，它是可以随意改变的。

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//.表示当前目录即工作目录</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//..表示当前目录的上一级目录</span>xtwy<span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@ubuntu</span>:~$ cd .xtwy<span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@ubuntu</span>:~$ cd ..xtwy<span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@ubuntu</span>:/home$ </code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li></ul>

（三） 删除目录 rmdir

rmdir是remove directory的简称，用于删除目录，它先删除目录下的所有文件，然后再删除该目录，但当目录下还有子目录时，该命令不能执行，需要使用rm命令，例如

<code class="hljs glsl has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//删除temp目录，先删除目录下的文件</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//再删除temp目录自身</span>root@ubuntu:/home/<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">max</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># rmdir temp/</span>root@ubuntu:/home/<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">max</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># rmdir literature/</span>rmdir: failed to remove `literature/': Directory <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">not</span> emptyroot@ubuntu:/home/<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">max</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># rm -r literature/</span>root@ubuntu:/home/<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">max</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># ls</span>demo  names</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li></ul>

其中rm -r中的r指的是递归的删除目录及目录中的文件，因此它具有很强的破坏力，要谨慎使用。

（四） 移动目录 mv

<code class="hljs coffeescript has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-regexp" style="color: rgb(0, 136, 0); box-sizing: border-box;">//</span>将目录demo移到<span class="hljs-regexp" style="color: rgb(0, 136, 0); box-sizing: border-box;">/home/xtwy/</span>目录下root<span class="hljs-property" style="box-sizing: border-box;">@ubuntu</span>:<span class="hljs-regexp" style="color: rgb(0, 136, 0); box-sizing: border-box;">/home/max# mv demo/</span> <span class="hljs-regexp" style="color: rgb(0, 136, 0); box-sizing: border-box;">/home/xtwy/</span>root<span class="hljs-property" style="box-sizing: border-box;">@ubuntu</span>:<span class="hljs-regexp" style="color: rgb(0, 136, 0); box-sizing: border-box;">/home/max# cd /home/xtwy/</span>root<span class="hljs-property" style="box-sizing: border-box;">@ubuntu</span>:/home/xtwy<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># ls</span>demo     Documents  examples.desktop  Pictures  TemplatesDesktop  Downloads  Music             Public    Videosroot<span class="hljs-property" style="box-sizing: border-box;">@ubuntu</span>:/home/xtwy<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># rmdir demo</span><span class="hljs-regexp" style="color: rgb(0, 136, 0); box-sizing: border-box;">//</span>原来目录的demo目录已经不存在了root<span class="hljs-property" style="box-sizing: border-box;">@ubuntu</span>:<span class="hljs-regexp" style="color: rgb(0, 136, 0); box-sizing: border-box;">/home/xtwy# cd /home/max/</span>root<span class="hljs-property" style="box-sizing: border-box;">@ubuntu</span>:/home/max<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># ls</span>names</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li></ul>

（五） 复制目录 cp

前面用mv命令移动目录，有时候需要对目录进行拷贝，使用方式如下：

<code class="hljs glsl has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//先创建一个演示目录，用-p，父目录如果不存在将会被创建</span>root@ubuntu:/home/<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">max</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># mkdir -p literature/demo</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//由于literature还包括子目录，此时拷贝不成功</span>root@ubuntu:/home/<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">max</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># cp literature/ /home/xtwy/</span>cp: omitting directory `literature/'<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//如果包括子目录的话，则加上-r参数，表示递归地拷贝</span>root@ubuntu:/home/<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">max</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># cp -r literature/ /home/xtwy/</span>root@ubuntu:/home/<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">max</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># cd /homt</span>bash: cd: /homt: No such file or directoryroot@ubuntu:/home/<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">max</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># cd /home/xtwy/</span>root@ubuntu:/home/xtwy<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># ls</span>Desktop    Downloads         literature  Pictures  TemplatesDocuments  examples.desktop  Music       Public    Videosroot@ubuntu:/home/xtwy<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># cd literature/</span>root@ubuntu:/home/xtwy/literature<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># ls</span>demo</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li></ul>

4. 文件操作

（一） 创建文件

直接通过命令行的方式创建文件的方式有多种，常用方式如下：

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">//通过echo命令，将输出的命令重定向到文件root@ubuntu:/home/xtwy<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># echo "hello linux" > hello.txt</span>root@ubuntu:/home/xtwy<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># ls</span>Desktop    Downloads         hello<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.txt</span>   Music     Public     VideosDocuments  examples<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.desktop</span>  literature  Pictures  Templates//touch命令，如何文件不存在，会创建文件root@ubuntu:/home/xtwy<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># touch hell1.txt</span>root@ubuntu:/home/xtwy<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># ls</span>Desktop    Downloads         hell1<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.txt</span>  literature  Pictures  TemplatesDocuments  examples<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.desktop</span>  hello<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.txt</span>  Music       Public    Videos</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li></ul>

（二） 显示文件内容

cate命令可以显示文件内容，它的全称是catenate，意思是将单词一个接一个地连接起来

<code class="hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:/home/xtwy</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># cat hello.txt </span>hello linux</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

cat命令会将文件中所有的内容全部一次性显示出现，例如

<code class="hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:/home/xtwy</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># cat /etc/profile</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># /etc/profile: system-wide .profile file for the Bourne shell (sh(1))</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># and Bourne compatible shells (bash(1), ksh(1), ash(1), ...).</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> [ -d /etc/profile.d ]; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">then</span>  <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> i <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">in</span> /etc/profile.d/*.sh; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">do</span>    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> [ -r <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$i</span> ]; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">then</span>      . <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$i</span>    fi  done  unset i  ......</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li></ul>

有时候我们希望能够分屏查看文件内容，此时可以使用less或more分页程序，less和more的使用方式相差不大，通过空格键显示下一屏信息，它们之间的差别在于less在文件末尾会显示END消息，而more直接返回shell终端，例如： 
less命令 

more命令 

（三） cp命令复制文件

<code class="hljs perl has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:<span class="hljs-regexp" style="color: rgb(0, 136, 0); box-sizing: border-box;">/home/xtwy</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># ls</span>Desktop    Downloads         hell1.txt  literature  Pictures  TemplatesDocuments  examples.desktop  hello.txt  Music       Public    Videos//复制文件root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:<span class="hljs-regexp" style="color: rgb(0, 136, 0); box-sizing: border-box;">/home/xtwy</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># cp hell1.txt literature/demo</span>root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:<span class="hljs-regexp" style="color: rgb(0, 136, 0); box-sizing: border-box;">/home/xtwy</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># cd literature/demo</span>//cd -返回上一次执行的工作目录root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:<span class="hljs-regexp" style="color: rgb(0, 136, 0); box-sizing: border-box;">/home/xtwy</span><span class="hljs-regexp" style="color: rgb(0, 136, 0); box-sizing: border-box;">/literature/demo</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># cd -</span>/home/xtwy</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li></ul>

需要注意的是cp命令在复制时，如果目标目录中已存在该文件，系统不会给出警告，而是直接覆盖，因此它可能存在销毁文件的风险，为解决这个问题可以使用-i参数让系统给出警告，例如：

<code class="hljs asciidoc has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">root@ubuntu:/home/xtwy# cp -i hell1.txt literature/democp: overwrite <span class="hljs-smartquote" style="box-sizing: border-box;">`literature/demo/hell1.txt'</span>? </code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

（三） mv命令移动或重命名文件

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">//在同一目录时，相当于文件重命名，执行完成后hell1<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.txt</span>不存在root@ubuntu:/home/xtwy<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># mv hell1.txt hell2.txt</span>root@ubuntu:/home/xtwy<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># ls</span>Desktop    Downloads         hell2<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.txt</span>  literature  Pictures  TemplatesDocuments  examples<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.desktop</span>  hello<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.txt</span>  Music       Public    Videos//移动hell2<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.txt</span>到literature/demoroot@ubuntu:/home/xtwy<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># mv hell2.txt literature/demo</span>root@ubuntu:/home/xtwy<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># cd literature/demo/</span>root@ubuntu:/home/xtwy/literature/demo<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># ls</span>hell1<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.txt</span>  hell2<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.txt</span>root@ubuntu:/home/xtwy/literature/demo<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># cd -</span>/home/xtwy//源目录hell2<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.txt</span>已不存在root@ubuntu:/home/xtwy<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># ls</span>Desktop    Downloads         hello<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.txt</span>   Music     Public     VideosDocuments  examples<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.desktop</span>  literature  Pictures  Templates</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li></ul>

（四）显示文件头部或尾部

显示文件头部内容用head命令，尾部用tail命令，默认显示行数为10

<code class="hljs vala has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">root@ubuntu:/home/xtwy# head ~/.bashrc <span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># ~/.bashrc: executed by bash(1) for non-login shells.</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># see /usr/share/doc/bash/examples/startup-files (in the package bash-doc)</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># for examples</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># If not running interactively, don't do anything</span>[ -z <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"$PS1"</span> ] && <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># don't put duplicate lines in the history. See bash(1) for more options</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># ... or force ignoredups and ignorespace</span>HISTCONTROL=ignoredups:ignorespaceroot@ubuntu:/home/xtwy# tail ~/.bashrcif [ -f ~/.bash_aliases ]; then    . ~/.bash_aliasesfi<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># enable programmable completion features (you don't need to enable</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># this, if it's already enabled in /etc/bash.bashrc and /etc/profile</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># sources /etc/bash.bashrc).</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">#if [ -f /etc/bash_completion ] && ! shopt -oq posix; then</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">#    . /etc/bash_completion</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">#fi</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li></ul>

head及tail的默认行数是可以修改的，例如：

<code class="hljs vala has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//仅显示前两行</span>root@ubuntu:/home/xtwy# head -<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span> ~/.bashrc <span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># ~/.bashrc: executed by bash(1) for non-login shells.</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;"># see /usr/share/doc/bash/examples/startup-files (in the package bash-doc)</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li></ul>

tail命令在查看日志文件内容增长时可能经常会使用，例如在hadoop启动之后，会产生许多日志，但出现问题时，可以采用tail命令动态地监测日志文件内容的增长，查看问题出在哪个地方。

<code class="hljs ruleslanguage has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//初始显示情况</span>root@ubuntu:/home/xtwy<span class="hljs-array" style="box-sizing: border-box;"># tail </span>-f hello.txt hello linux<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//向文件中追加内容</span>root@ubuntu:/home/xtwy<span class="hljs-array" style="box-sizing: border-box;"># echo </span><span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"hello linux linux"</span> >> hello.txt<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//追加后的输出情况</span>root@ubuntu:/home/xtwy<span class="hljs-array" style="box-sizing: border-box;"># tail </span>-f hello.txt hello linuxhello linux linux</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li></ul>

（五）其它常见文件操作命令

下面的命令都不会改变文件内容

<code class="hljs mel has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:/home/xtwy# cp hello.txt hello1.txtroot<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:/home/xtwy# <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">ls</span>Desktop    Downloads         hello1.txt  literature  Pictures  TemplatesDocuments  examples.desktop  hello.txt   Music       Public    Videos<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//根据文件内容排序</span>root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:/home/xtwy# <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">sort</span> hello1.txthello linuxhello linux linux<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//逆序输出</span>root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:/home/xtwy# <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">sort</span> -r  hello1.txthello linux linuxhello linux<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//diff进行内容比较</span>root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:/home/xtwy# diff hello1.txt hello.txt<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//向文件中追加内容</span>root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:/home/xtwy# echo <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"hello linux linux"</span> >> hello.txt<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//内容比较</span>root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:/home/xtwy# diff hello1.txt hello.txt<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>a3> hello linux linux<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//格式化输出</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//-u参数将文件分成多块</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//比较的两个文件分别用-、+表示</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//本例中 -表示hello1.txt，+表示hello.txt</span>root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@ubuntu</span>:/home/xtwy# diff -u hello1.txt hello.txt--- hello1.txt  <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2015</span>-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">08</span>-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">22</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">17</span>:<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">28</span>:<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">44.071202558</span> -<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0700</span>+++ hello.txt   <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2015</span>-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">08</span>-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">22</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">17</span>:<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">29</span>:<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">49.131181281</span> -<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0700</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//@@xxx@@用于标识行起始编号、行数</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//-1,2表示 hello1.txt文件起始编号为1，行数为2</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//+1,3表示 hello.txt文件起始编号为1，行数为3</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@@</span> -<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span> +<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">3</span> <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@@</span> hello linux hello linux linux+hello linux linux</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li></ul>

内容来源： http://blog.csdn.net/lovehuangjiaju/article/details/47856591