0063-0065.html

来自「linux-unix130.linux.and.unix.ebooks130 l」· HTML 代码 · 共 268 行

HTML
268 行
字号 




<HTML>

<HEAD>

<TITLE>Sams Teach Yourself Linux in 24 Hours:Manipulation and Searching Commands:EarthWeb Inc.-</TITLE>

<META NAME="ROBOTS" CONTENT="NOINDEX, NOFOLLOW">
<SCRIPT>
<!--
function displayWindow(url, width, height) {
        var Win = window.open(url,"displayWindow",'width=' + width +
',height=' + height + ',resizable=1,scrollbars=yes');
}
//-->
</SCRIPT>
</HEAD>

 -->




<!-- ISBN=0672311623 //-->

<!-- TITLE=Sams Teach Yourself Linux in 24 Hours//-->

<!-- AUTHOR=Bill Ball//-->

<!-- PUBLISHER=Macmillan Computer Publishing//-->

<!-- IMPRINT=Sams//-->

<!-- CHAPTER=05 //-->

<!-- PAGES=0063-0082 //-->

<!-- UNASSIGNED1 //-->

<!-- UNASSIGNED2 //-->







<P><CENTER>

<a href="../ch04/0059-0062.html">Previous</A> | <a href="../ewtoc.html">Table of Contents</A> | <a href="0066-0068.html">Next</A>

</CENTER></P>



<A NAME="PAGENUM-63"><P>Page 63</P></A>







<H3><A NAME="ch05_ 2">Hour 5</A></H3>



<H2>

<A NAME="ch05_ 3">

Manipulation and Searching<BR>

Commands

</A>

</H2>



<P>In this hour, you'll learn about creating, copying, deleting, and moving

files and directories. You'll also learn about searching through files and how

to compress and uncompress files. This information will build on

information you've learned in the last hour, and the commands you learn here will be

used later on in this book.

</P>



<H3><A NAME="ch05_ 4">

Manipulating Files or Directories

</A></H3>



<P>Using Linux isn't different from any other computer operating system.

You create, delete, and move files on your hard drive in order to organize

your information and manage how your system works or looks. This section

shows you how to do these tasks quickly and easily.

</P>



<P>Although the graphical interface for Linux, the X Window

System, may offer drag and drop or multiple selections in order to copy or delete files, many

of the commands you'll learn here form the base of these operations. It is

worth knowing how these programs work, even if you don't use Linux in the

console mode.

</P>



<A NAME="PAGENUM-64"><P>Page 64</P></A>







<H4><A NAME="ch05_ 5">

Creating Files with the touch Command

</A></H4>



<P>The touch command is easy to use, and generally, there are two reasons to use it. The

first reason is to create a file, and the second is to update a file's modification date. The

touch command is part of the GNU file utilities package, and has several options.

</P>



<P>To create a file with touch, use

</P>



<!-- CODE SNIP //-->

<PRE>

# touch newfile

# ls -l newfile

-rw-rw-r--   1 bball    bball           0 Nov 13 08:50 newfile

</PRE>

<!-- END CODE SNIP //-->



<P>As you can see, touch created a file with a length, or size, of zero. You can also use

</P>



<!-- CODE SNIP //-->

<PRE>

# &gt; newfile2

# ls -l new*

-rw-rw-r--   1 bball    bball           0 Nov 13 08:50 newfile

-rw-rw-r--   1 bball    bball           0 Nov 13 08:54 newfile2

</PRE>

<!-- END CODE SNIP //-->



<P>Like touch, this creates a file with a length of zero. So why use

touch, if you can do this at the command line? Because

touch will update a file's date or time. You can even use

touch to change a file's date or time to the past or the future, for example:

</P>



<!-- CODE SNIP //-->

<PRE>

# touch newfile2

# ls -l newfile2

-rw-rw-r--   1 bball    bball           0 Nov 13 09:04 newfile2

</PRE>

<!-- END CODE SNIP //-->



<P>As you can see, the file newfile2 now has a timestamp 10 minutes younger. You can also

set the time and date of a file to an arbitrary date, for example:

</P>



<!-- CODE SNIP //-->

<PRE>

# touch -t 1225110099 newfile2

# ls -l &#151;full-time new*

-rw-rw-r--   1 bball    bball           0 Thu Nov 13 08:50:00 1997 newfile

-rw-rw-r--   1 bball    bball           0 Sat Dec 25 11:00:00 1999 newfile2

</PRE>

<!-- END CODE SNIP //-->



<P>Using the --full-time option and long format listing of the

ls command shows that the file newfile2 now has a timestamp of 11 a.m., Christmas Day, 1999 (which appears to be, and is

indeed, a Saturday).

</P>



<P>One use for touch is during backup operations.

Either before or after backing up a series of files or directories, you can use

touch to update the timestamps of your files so that

the backup program has a reference time for the next backup session. Another use for

touch is to control deletion or retention of log files during the next automated file cleanup

by scheduled programs managed by cron (see &quot;Using the

cron Daemon&quot; in Hour 24, &quot;Scheduling&quot;). If you make a log file old enough, it will be deleted. If you update it,

the file will be retained.

</P>



<H4><A NAME="ch05_ 6">

Deleting Files with the rm Command

</A></H4>



<P>The rm command deletes files. This command has several simple options, but should

be used cautiously. Why? Because when rm deletes a file, it is gone (you may be able to

recover

</P>



<A NAME="PAGENUM-65"><P>Page 65</P></A>





<P>

portions of text files, though; see the mc command or the Command Reference section

for pointers).

</P>



<P>Always running Linux while logged in as the root

operator and using the rm command has caused many untold tales of woe and grief. Why? Because with one simple command

you can wipe out not only your Linux system, but also any mounted filesystems, including

DOS partitions, flash RAM cards, or removable hard drives, as follows:

</P>



<!-- CODE SNIP //-->

<PRE>

# rm -fr /*

</PRE>

<!-- END CODE SNIP //-->



<P>This command removes all files and directories recursively (with the

-r option), starting at the root or / directory. If you must run Linux as root, make sure to back up your

system, and read Hour 23, &quot;Archiving.&quot;

</P>



<P>The rm command will delete one or several files from the command line. You can use

any of the following:

</P>



<!-- CODE SNIP //-->

<PRE>

# rm file

# rm file1 file2 file2

# rm file*

</PRE>

<!-- END CODE SNIP //-->



<P>One of the safer ways to use rm is through the

-i or interactive option, where you'll be asked if you want to delete the file, for example:

</P>



<!-- CODE SNIP //-->

<PRE>

# rm -i new*

rm: remove `newfile'? y

rm: remove `newfile2'? y

</PRE>

<!-- END CODE SNIP //-->



<P>You can also force file deletion by using the

-f option, as in

</P>



<!-- CODE SNIP //-->

<PRE>

# rm -f new*

</PRE>

<!-- END CODE SNIP //-->



<P>However, if rm finds a directory, even if it is empty, it will not delete the directory,

and complains, even if you use -f, as in the following:

</P>



<!-- CODE SNIP //-->

<PRE>

# rm -f temp*

rm: temp: is a directory

rm: temp2: is a directory

</PRE>

<!-- END CODE SNIP //-->



<P>When you combine -f and -r, the recursive option, you can delete directories and all

files or directories found within (if you own them; see Hour 21, &quot;Handling Files&quot;), as in

the following example:

</P>



<!-- CODE SNIP //-->

<PRE>

# rm -fr temp*

</PRE>

<!-- END CODE SNIP //-->



<P>The -fr option also makes rm act like the rmdir command (discussed later in this chapter).

Use this option with caution!

</P>



<P>Some X Window managers, such as CDE, or utilities, such as TkDesk, offer &quot;trash

can&quot; approaches to deleting files, but the files are not really deleted, just moved to a

temporary

</P>



<P><CENTER>

<a href="../ch04/0059-0062.html">Previous</A> | <a href="../ewtoc.html">Table of Contents</A> | <a href="0066-0068.html">Next</A>

</CENTER></P>











</td>
</tr>
</table>

<!-- begin footer information -->









</body></html>

0063-0065.html - 源码说明

本页面展示了「linux-unix130.linux.and.unix.ebooks130 linux and unix ebookslinuxLearning Linux - Collection of 12 E」中的 0063-0065.html 源码文件，采用 HTML 编程语言编写，共 268 行代码。您可以在线阅读完整代码内容，也可以返回资源详情页下载完整源码包进行本地学习和开发。

虫虫下载站收录了大量与linux相关的技术资源，包括源代码、技术文档、电路图等，是电子工程师和嵌入式开发者的专业学习平台。

⌨️ 快捷键说明

复制代码Ctrl + C
搜索代码Ctrl + F
全屏模式F11
增大字号Ctrl + =
减小字号Ctrl + -
显示快捷键?