How to create a link in Linux

- 日理万妓 2022-06-15 01:29 358阅读 0赞

# 查漏补缺旧知识：    #

# How to create a link in Linux #

Updated: 04/26/2017 by Computer Hope

In your [ Linux][Linux] [ file system][file system], a **link** is a connection between a [ file name][file name] and the actual [ data][data] on the [ disk][disk]. There are two main types of links that can be created: [ "hard" links][_hard_ links], and "soft" or [ symbolic links][symbolic links]. Hard links are low-level links which the system uses to create elements of the file system itself, such as [files][] and [directories][].

Users typically do not want to create or modify hard links themselves, but symbolic links are a useful tool for any Linux user. A symbolic link is a special file that points to another file or directory, which is called the **target**. Once created, a symbolic link can be treated as if it is the target file, even if it is has a different name and is located in another directory. Multiple symbolic links can even be created to the same target file, allowing the target to be accessed by multiple names.

The symbolic link is a file in its own right, but it does not contain a copy of the target file's data. It is similar to a [shortcut][] in [Microsoft Windows][]: if you delete a symbolic link, the target is unaffected. Also, if the target of a symbolic link is deleted, moved, or renamed, the symbolic link is not updated. When this happens, the symbolic link is called "broken" or "orphaned", and will no longer function as a link.

## How to create symbolic links using a file manager ##

One easy way to create a symbolic link from within the [ X Windows][X Windows] [ GUI][GUI] is with your [ file manager][file manager]. Different Linux [ distributions][distributions] use different file managers, but the process is similar. Locate a target file in your file manager GUI, highlight it by clicking on it once, and select the option "create a link." This option is usually found under the Edit menu, or in the [context menu][] that appears when you [right-click][] the highlighted file.

![Creating symbolic links with a Linux file manager][]

In the example shown above, using the Thunar file manager, we have highlighted the file **myfile.txt**, then selected **Make Link...** in the  **Edit** menu. After completed a new symbolic link called **link to myfile.txt** is created. This link can be [renamed][] or moved to another location, and it will always point to our target (unless the target is later moved or deleted, in which case the link will become orphaned).

## How to create symbolic links from the command line ##

The [ command line][command line] is a powerful tool in Linux because it gives you greater control over your commands. (For more information about the command line, and how to access it from within Linux, see our [Linux and Unix shell tutorial][]).

You can create symbolic links using the [ **ln**][_ln] command's **-s** option. The general [ syntax][syntax] for creating a symbolic link is:

ln -s target linkname

For instance, if we have a file in our [ working directory][working directory] called **myfile.txt**, and we want to create a symbolic link in the same directory called **mylink**, we could use the command:

ln -s myfile.txt mylink

Let's see what this will look like on the command line. Here, we have opened a [terminal][] session that places us at our [shell][]'s [command prompt][]. We are logged in a system named **myhost** as a user named **user**, and our working directory is a folder in our [home directory][] called **myfolder**:

First, let's use [ **ls**][_ls] with the **-l** option to produce a long list of all the files in our directory:

![output of command: ls -l][output of command_ ls -l]

We see our file, **myfile.txt**, which is the only file in the directory. ("**total 4**" refers to how many [blocks][] on the disk are used by the files listed, not the total number of files).

Let's use the [ **cat**][_cat] command to view the contents of **myfile.txt**:

![output of command: cat myfile.txt][output of command_ cat myfile.txt]

Now, let's create a symbolic link to **mylink.txt** called **mylink** using the **ln -s** command:

![ln -s myfile.txt mylink][]

It seems like nothing happened, but this means it worked as expected. If there was an error, or if an unexpected condition was encountered, we would receive a notification.

Now, if we do another **ls -l**, we see two files — our target and our link:

![output of command: ls -l, displaying link and target][output of command_ ls -l_ displaying link and target]

One of the benefits of doing a long listing with "**-l**" is that we see extra information in addition to the file name. Notice the "**l**" at the beginning of the line containing our link name, indicating that the file is a symbolic link. Also, notice that after **mylink** is the "**->**" symbol, followed by the name of the target. In our above example the color blue; most shells, by default, are configured to display certain file types in different colors, but your terminal might show different colors or none at all.

Now let's use our symbolic link. If we run **cat** on it, it displays the contents of **myfile.txt**:

![output of cat command][]

We can rename our link with [ **mv**][_mv], and it still points to the same target:

![Renamed symbolic links still function properly.][]

But what happens if we move our link somewhere else? In this case, our link will break. We can see this by making a new directory with [**mkdir**][mkdir], and moving the link into the new directory with **mv**:

![Moving the link to another location breaks the link, because the link did not specify an absolute path][Moving the link to another location breaks the link_ because the link did not specify an absolute path]

You can see that when we view the contents of directory **newfolder** with **ls -l**, our link is highlighted in red, indicating that it points to a file that is not there. And if we try to **cat** the contents of the link, the shell informs us that the file does not exist. This error occurs because the link points to "**myfile.txt**" with no other [path][] information. Therefore, the operating system will always look for **myfile.txt** in whatever directory the link happens to be in at the moment.

Let's start over by [ removing][removing] **newfolder** and its contents using the command **[rm][] \-r**:

![starting over][]

This time, let's create the symbolic link using the [ absolute path][absolute path] to **myfile.txt**. Let's double check the name of our working directory with [**pwd**][pwd]:

![output of command "pwd"][output of command _pwd]

Our working directory is **/home/user/myfolder**, so let's include this in the target name when we create the link:

![Creating a symbolic link using an absolute path in the target name.][]

As you can see from the output of **ls -l**, our link now points to the file **/home/user/myfolder/myfile.txt**. With this path information, we can move the link to another location, and it will still point to our target:

![Our symbolic link, which points to an absolute path name, works even when moved to a new location.][Our symbolic link_ which points to an absolute path name_ works even when moved to a new location.]

Tip: Your [ **bash**][_bash] shell keeps an [ environment variable][environment variable] called **$PWD** that always stores the value of your working directory. You can use this variable to insert the full path before your target name, as long as the target is in your working directory. We can view the value of **$PWD** using the **echo** command:

![Checking the value of the $PWD environment variable][Checking the value of the _PWD environment variable]

This text is inserted if we use **$PWD** as part of a command. It is a good idea to enclose it in quotes as **"$PWD"** in case the directory name has any spaces. The quotes make sure the shell knows they are part of the pathname and not command separators.

Here is our command, and a directory listing to show that it worked:

![Using the $PWD environment variable to create a symbolic link.][Using the _PWD environment variable to create a symbolic link.]

Notice that we also put a slash ("**/**") directly between **"$PWD"** and **myfile.txt** to complete the full path name.

### Additional information ###

*  [How do I get into the command line shell?][Linux and Unix shell tutorial]
 *  [ln command][_ln] description, syntax, options, and examples

转自https://www.computerhope.com/issues/ch001638.html

[Linux]: https://www.computerhope.com/jargon/l/linux.htm
[file system]: https://www.computerhope.com/jargon/f/filesyst.htm
[file name]: https://www.computerhope.com/jargon/f/filename.htm
[data]: https://www.computerhope.com/jargon/d/data.htm
[disk]: https://www.computerhope.com/jargon/d/disk.htm
[_hard_ links]: https://www.computerhope.com/jargon/h/hardlink.htm
[symbolic links]: https://www.computerhope.com/jargon/s/symblink.htm
[files]: https://www.computerhope.com/jargon/f/file.htm
[directories]: https://www.computerhope.com/jargon/d/director.htm
[shortcut]: https://www.computerhope.com/jargon/s/shortcut.htm
[Microsoft Windows]: https://www.computerhope.com/jargon/w/windows.htm
[X Windows]: https://www.computerhope.com/jargon/x/xwin.htm
[GUI]: https://www.computerhope.com/jargon/g/gui.htm
[file manager]: https://www.computerhope.com/jargon/f/filemana.htm
[distributions]: https://www.computerhope.com/jargon/v/variant.htm
[context menu]: https://www.computerhope.com/jargon/p/popupmen.htm
[right-click]: https://www.computerhope.com/jargon/r/righclic.htm
[Creating symbolic links with a Linux file manager]: https://www.computerhope.com/issues/pictures/linux-create-link-gui-horiz-composite.jpg
[renamed]: https://www.computerhope.com/jargon/r/rename.htm
[command line]: https://www.computerhope.com/jargon/c/commandi.htm
[Linux and Unix shell tutorial]: https://www.computerhope.com/issues/chshell.htm
[_ln]: https://www.computerhope.com/unix/uln.htm
[syntax]: https://www.computerhope.com/jargon/s/syntax.htm
[working directory]: https://www.computerhope.com/jargon/c/currentd.htm
[terminal]: https://www.computerhope.com/jargon/t/terminal.htm
[shell]: https://www.computerhope.com/jargon/s/shell.htm
[command prompt]: https://www.computerhope.com/jargon/c/commprom.htm
[home directory]: https://www.computerhope.com/jargon/h/homedir.htm
[_ls]: https://www.computerhope.com/jargon/l/ls.htm
[output of command_ ls -l]: https://www.computerhope.com/issues/pictures/linux-create-link-cmdline-02.gif
[blocks]: https://www.computerhope.com/jargon/b/block.htm
[_cat]: https://www.computerhope.com/jargon/c/cat.htm
[output of command_ cat myfile.txt]: https://www.computerhope.com/issues/pictures/linux-create-link-cmdline-03.gif
[ln -s myfile.txt mylink]: https://www.computerhope.com/issues/pictures/linux-create-link-cmdline-04.gif
[output of command_ ls -l_ displaying link and target]: https://www.computerhope.com/issues/pictures/linux-create-link-cmdline-05.gif
[output of cat command]: https://www.computerhope.com/issues/pictures/linux-create-link-cmdline-06.gif
[_mv]: https://www.computerhope.com/unix/umv.htm
[Renamed symbolic links still function properly.]: https://www.computerhope.com/issues/pictures/linux-create-link-cmdline-07.gif
[mkdir]: https://www.computerhope.com/jargon/m/mkdir.htm
[Moving the link to another location breaks the link_ because the link did not specify an absolute path]: https://www.computerhope.com/issues/pictures/linux-create-link-cmdline-08.gif
[path]: https://www.computerhope.com/jargon/p/path.htm
[removing]: https://www.computerhope.com/jargon/d/delete.htm
[rm]: https://www.computerhope.com/unix/urm.htm
[starting over]: https://www.computerhope.com/issues/pictures/linux-create-link-cmdline-09.gif
[absolute path]: https://www.computerhope.com/jargon/a/absopath.htm
[pwd]: https://www.computerhope.com/jargon/p/pwd.htm
[output of command _pwd]: https://www.computerhope.com/issues/pictures/linux-create-link-cmdline-10.gif
[Creating a symbolic link using an absolute path in the target name.]: https://www.computerhope.com/issues/pictures/linux-create-link-cmdline-11.gif
[Our symbolic link_ which points to an absolute path name_ works even when moved to a new location.]: https://www.computerhope.com/issues/pictures/linux-create-link-cmdline-12.gif
[_bash]: https://www.computerhope.com/unix/ubash.htm
[environment variable]: https://www.computerhope.com/jargon/e/envivari.htm
[Checking the value of the _PWD environment variable]: https://www.computerhope.com/issues/pictures/linux-create-link-cmdline-13.gif
[Using the _PWD environment variable to create a symbolic link.]: https://www.computerhope.com/issues/pictures/linux-create-link-cmdline-14.gif