Spark修煉之道（基礎篇）——Linux大資料開發基礎：第二節：Linux檔案系統、目錄（一）

本節主要內容

1. 如何獲取幫助文件
2. Linux檔案系統簡介
3. 目錄操作
4. 訪問許可權

1. 如何獲取幫助文件

在實際工作過程當中，經常會忘記命令的使用方式，例如ls命令後面可以跟哪些引數，此時可以使用man命令來檢視其使用方式，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命令獲取命令幫助手冊</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>

可以使用鍵盤上的 來顯示下一行或上一行命令，也可以使用 進行上一頁或下一頁（屏）命令的檢視，另外 空格鍵也可以用來顯示下一屏的命令。想退出命令檢視，直接按q鍵退出即可，也可以h鍵顯示less命令列表（man命令通過less命令輸出結果）

2. Linux檔案系統簡介

（一） 檔案和目錄

本節從使用者的角度來介紹Linux檔案系統，Linux根據檔案形式將檔案分為目錄和普通檔案，如下圖： 
 
目錄或檔案的名稱長度不超過255個字元，檔案或目錄名可由下列字元構成：

• Uppercase letters (A–Z)
• Lowercase letters (a–z)
• Numbers (0–9)
• Underscore ( _ )
• Period(.)
• Comma(,） 
  檔案或目錄名區分大小寫，屬於不同的檔案或目錄

（二） 副檔名與不可見檔名

與Window作業系統有很大不同的是，Linux檔案對副檔名沒有強制要求，例如假設編寫了一個c語言原始檔，你可以將其命名為complier.c，也可以是其它如complier、complier.ccc等檔名，但不推薦這麼做，因為如果能將副檔名與特定的檔案進行關聯的話，有利於理解檔案內容，目前約定成俗的linux副檔名如下表：

帶副檔名的檔名	副檔名的含義
max.c	C語言原始檔
max.o	編碼後的目的碼檔案
max	max.c對應的可執行檔案
memo.txt	文字檔案
memo.pdf	pdf檔案，必須在GUI介面上使用xpdf或kpdf才能檢視
memo.ps	PostScript檔案，必須在GUI介面上使用ghostscript或kpdf才能檢視
memo.z	經壓縮程式壓縮後的檔案，可使用uncompress或gunzip解壓
memo.gz	經gzip壓縮程式壓縮後的檔案，可使用gunzip解壓
memo.tar.gz或memo.tgz	經gzip壓縮後的tar歸檔檔案,可使用gunzip解壓
memo.bz2	經bzip2壓縮後的檔案,可使用bunzip2解壓
memo.html	html檔案，使用GUI環境的firefox檢視
memo.jpg等	影象檔案,使用GUI環境的照片檢視器開啟

在前一講中我們看到，linux中還存在大量的隱藏檔案，採用ls -a 命令可以顯示，想定義隱藏檔案，只要檔名或目錄以.開始即可 

（三） 絕對路徑與相對路徑

在Linux中絕對路徑與相對路徑是一個很重要的概念，下圖給出了什麼是絕對路徑 
 
所有以根目錄”/”作為開始的都是絕對路徑，其它的均為相對路徑

<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;">//絕對路徑訪問</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;">//相對路徑訪問</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. 目錄操作

（一） 建立目錄 mkdir

為演示方便，使用下列目錄結構進行演示：

1 絕對路徑建立方式

<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;">//使用絕對路徑建立</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>  xtwy
root<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 相對路徑建立方式

<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;">//使用相對路徑進行建立</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>/names
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>/temp
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>/literature
root<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 demo
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># <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>

有時不想層層目錄建立，此時可以在mkdir 後面加上引數 -p（parents），將父子目錄一起建立

<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  temp
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;"># 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） 更改目錄 cd

工作目錄與主目錄的區別 
使用者每次登入後的預設目錄就是主目錄，與系統會話期間保持不變，主目錄用~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>

工作目錄又稱當前目錄，cd命令執行完成後的目錄就是工作目錄，它是可以隨意改變的。

<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;">//.表示當前目錄即工作目錄</span>
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//..表示當前目錄的上一級目錄</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） 刪除目錄 rmdir

rmdir是remove directory的簡稱，用於刪除目錄，它先刪除目錄下的所有檔案，然後再刪除該目錄，但當目錄下還有子目錄時，該命令不能執行，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;">//刪除temp目錄，先刪除目錄下的檔案</span>
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//再刪除temp目錄自身</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> empty
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;"># 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指的是遞迴的刪除目錄及目錄中的檔案，因此它具有很強的破壞力，要謹慎使用。

（四） 移動目錄 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>將目錄demo移到<span class="hljs-regexp" style="color: rgb(0, 136, 0); box-sizing: border-box;">/home/xtwy/</span>目錄下
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  Templates
Desktop  Downloads  Music             Public    Videos
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;"># rmdir demo</span>
<span class="hljs-regexp" style="color: rgb(0, 136, 0); box-sizing: border-box;">//</span>原來目錄的demo目錄已經不存在了
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） 複製目錄 cp

前面用mv命令移動目錄，有時候需要對目錄進行拷貝，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;">//先建立一個演示目錄，用-p，父目錄如果不存在將會被建立</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;">//由於literature還包括子目錄，此時拷貝不成功</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;">//如果包括子目錄的話，則加上-r引數，表示遞迴地拷貝</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 directory
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 /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  Templates
Documents  examples.desktop  Music       Public    Videos
root@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. 檔案操作

（一） 建立檔案

直接通過命令列的方式建立檔案的方式有多種，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;">//通過echo命令，將輸出的命令重定向到檔案
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     Videos
Documents  examples<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.desktop</span>  literature  Pictures  Templates
//touch命令，如何檔案不存在，會建立檔案
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  Templates
Documents  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） 顯示檔案內容

cate命令可以顯示檔案內容，它的全稱是catenate，意思是將單詞一個接一個地連線起來

<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命令會將檔案中所有的內容全部一次性顯示出現，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>

有時候我們希望能夠分屏檢視檔案內容，此時可以使用less或more分頁程式，less和more的使用方式相差不大，通過空格鍵顯示下一屏資訊，它們之間的差別在於less在檔案末尾會顯示END訊息，而more直接返回shell終端，例如： 
less命令 

more命令 

（三） cp命令複製檔案

<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  Templates
Documents  examples.desktop  hello.txt  Music       Public    Videos
//複製檔案
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 -返回上一次執行的工作目錄
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命令在複製時，如果目標目錄中已存在該檔案，系統不會給出警告，而是直接覆蓋，因此它可能存在銷燬檔案的風險，為解決這個問題可以使用-i引數讓系統給出警告，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/demo
cp: 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命令移動或重新命名檔案

<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;">//在同一目錄時，相當於檔案重新命名，執行完成後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  Templates
Documents  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
//移動hell2<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.txt</span>到literature/demo
root@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
//源目錄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     Videos
Documents  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）顯示檔案頭部或尾部

顯示檔案頭部內容用head命令，尾部用tail命令，預設顯示行數為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:ignorespace
root@ubuntu:/home/xtwy# tail ~/.bashrc
if [ -f ~/.bash_aliases ]; then
    . ~/.bash_aliases
fi

<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的預設行數是可以修改的，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;">//僅顯示前兩行</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命令在檢視日誌檔案內容增長時可能經常會使用，例如在hadoop啟動之後，會產生許多日誌，但出現問題時，可以採用tail命令動態地監測日誌檔案內容的增長，檢視問題出在哪個地方。

<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;">//初始顯示情況</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;">//向檔案中追加內容</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;">//追加後的輸出情況</span>
root@ubuntu:/home/xtwy<span class="hljs-array" style="box-sizing: border-box;"># tail </span>-f hello.txt 
hello 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></ul>

（五）其它常見檔案操作命令

下面的命令都不會改變檔案內容

<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.txt
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;">ls</span>
Desktop    Downloads         hello1.txt  literature  Pictures  Templates
Documents  examples.desktop  hello.txt   Music       Public    Videos
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//根據檔案內容排序</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.txt
hello linux
hello linux linux
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//逆序輸出</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.txt
hello linux linux
hello linux
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//diff進行內容比較</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;">//向檔案中追加內容</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;">//內容比較</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;">//格式化輸出</span>
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//-u引數將檔案分成多塊</span>
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//比較的兩個檔案分別用-、+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@@用於標識行起始編號、行數</span>
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//-1,2表示 hello1.txt檔案起始編號為1，行數為2</span>
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//+1,3表示 hello.txt檔案起始編號為1，行數為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>

內容來源： http://blog.csdn.net/lovehuangjiaju/article/details/47856591