Shulou(Shulou.com)06/01 Report--

This article mainly introduces "how to use the ln command in Linux to establish a connection between files". In daily operation, I believe many people have doubts about how to use the ln command in Linux to establish a connection between files. Xiaobian consulted all kinds of materials and sorted out a simple and easy-to-use method of operation. I hope it will be helpful to answer the question of "how to use the ln command in Linux to establish a connection between files". Next, please follow the editor to study!

In the Unix world, there are two concepts of link', generally called hard connection and soft connection. A hard connection is just a file name. A file can have several file names, and the file can be deleted only if the last file name is deleted from disk. The number of file names is determined by ls (1). All filenames are in the same state, so there is no such thing as the lq source name rq. Usually all the names of a file in the file system contain the same data information, but this is not necessary. A soft connection (or symbolic connection) is completely different: it is a small specified file that contains path information. As a result, soft connections can point to files in different file systems (such as text on different machine file systems mounted by NFS), or even to a file that does not necessarily exist. When the soft connection file is accessed (system calls open (2) or stat (2)), the operating system replaces the access point of the file with the path contained in the file, thereby realizing access to the specified file. (use the commands rm (1) and unlink (2) to delete the connection, but not the file that the file points to. The system specifies that lstat (2) and readlink (2) are called to read the status of the connection file and the file it refers to. Whether to operate on the soft connection file or the directed file is different because there are different system calls in different operating system components. )

Ln creates connections between files. By default, a hard connection is generated, and with the-s option, a symbolic (soft) connection is generated.

If only one file name is given, ln will generate a connection to the file in the current directory, that is, a connection in the current directory (within the GNU range) with the same name as the file (the last). If the last parameter is an existing directory name, ln will give each source file in that directory to generate a connection with the same file name as the source file, (for different cases, see the description of no-dereference below); if only two file names are given, ln will generate a connection to the source file; if the last parameter is not a directory name or more than two file names, an error will be reported.

By default, ln does not delete existing files or symbolic links. (therefore, it can be used to lock the target file, that is, when dest no longer exists.) but the option-f can be enforced.

In existing implementations, only superusers can establish hard connections to directories. POSIX forbids system calls to link (2) and ln to establish hard connections to directories (but allows hard connections between different file systems).

Usage: ln [options] source dist, where the format of option is:

[- bdfinsvF] [- S backup-suffix] [- V {numbered,existing,simple}] [--help] [--version] [-]

Description: Linux/Unix file system, there are so-called link (link), we can regard it as an alias for the file, and links can be divided into two types: hard link (hard link) and soft link (symbolic link), hard link means that a file can have multiple names, while the way of soft link is to generate a special file, the content of the file points to the location of another file. Hard links exist in the same file system, while soft links can span different file systems.

Ln source dist generates a dist to source, while the use of hard or soft links is determined by parameters.

Neither hard link nor soft link will make a copy of the original file and will only take up a very small amount of disk space.

-f: delete files with the same name as dist when linking

-d: allows system administrators to hard-link their own directories

-I: ask before deleting files with the same name as dist

-n: treat dist as a general file when making soft links

-s: soft link (symbolic link)

-v: show its file name before the link

-b: back up files that will be overwritten or deleted when linked

-S SUFFIX: add the suffix SUFFIX to all the backed-up files

-V METHOD: specify the backup method

-- help: displays auxiliary instructions

-- version: display version

Note:

If you do not use the-s flag, you cannot link files between file systems.

If TargetDirectory is already a symbolic link to a directory, the ln command treats the existing target as a file. This means that a command like ln-fs somepath/lname symdir does not follow the existing symdir symbolic link and instead creates a new symbolic link from somepath/lname to symdir.

Exit statu

This command returns the following exit values:

All specified files have been successfully linked.

An error occurred in > 0.

Example:

The code is as follows:

[root@localhost test_ln] # ln-s / home/zhangy/heartbeat. / # establish a soft connection to heartbeat in the current directory

[root@localhost test_ln] # ln-s / home/zhangy/test. / # Software connection for establishing directory

[root@localhost test_ln] # ln / home/zhangy/tee.txt. / # establish a hard connection

[root@localhost test_ln] # ll

Total 4

Lrwxrwxrwx 1 root root 22 05-11 11:04 heartbeat-> / home/zhangy/heartbeat # File Software connection

-rw-r--r-- 2 root root 0 2010-11-24 tee.txt # file hard connection

Lrwxrwxrwx 1 root root 17 05-11 11:04 test-> / home/zhangy/test # directory software connection

1. To create another link (alias) to a file, enter:

The code is as follows:

Ln-f chap1 intro

This links chap1 to the new name, intro. If intro does not exist, the file name is created. If intro already exists, the file will be replaced with a link to chap1. Then the chap1 and intro filenames point to the same file. Changes to any one of them will appear in the other. If a file name is deleted by the rm command, the file is not completely deleted because it still exists under another name.

two。 To link the file to the same name in another directory, enter:

The code is as follows:

Ln index manual

This links index to the new name, manual/index.

Note: intro in example 1 is the name of a file; manual in example 2 is an existing directory.

3. To link several files to names in another directory, enter:

The code is as follows:

Ln chap2 jim/chap3 / home/manual

This links chap2 to the new name / home/manual/chap2; and jim/chap3 to the new name / home/manual/chap3.

4. If you want to use pattern matching characters in the ln command, enter:

The code is as follows:

Ln manual/*.

This links all files in the manual directory to the current directory,. (click), give them the same name in the manual directory.

Note: you must enter a space between the asterisk and the period.

5. To create a symbolic link, type:

The code is as follows:

Ln-s / tmp/toc toc

This creates a symbolic link toc in the current directory. The toc file points to the / tmp/toc file. If the / tmp/toc file already exists, the cat toc command can list its contents.

6. If you want the same result without specifying the TargetFile parameter, enter:

The code is as follows:

Ln-s / tmp/toc

At this point, the study on "how to use the ln command in Linux to establish a connection between files" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.