Linux shell command ln All In One
硬連接 vs 軟連接
hard link
symbolic link
https://www.gnu.org/software/coreutils/ln
In the 1st form, create a link to TARGET with the name LINK_NAME.
In the 2nd form, create a link to TARGET in the current directory.
In the 3rd and 4th forms, create links to each TARGET in DIRECTORY.
Create hard links by default, symbolic links with --symbolic.
By default, each destination (name of new link) should not already exist.
When creating hard links, each TARGET must exist.
Symbolic links can hold arbitrary text;
if later resolved, a relative link is interpreted in relation to its parent directory.
Mandatory arguments to long options are mandatory for short options too.
在第一種形式中，使用名稱 LINK_NAME 創建指向 TARGET 的鏈接。
在第二種形式中，在當前目錄中創建指向 TARGET 的鏈接。
在第 3 和第 4 種形式中，創建指向 DIRECTORY 中每個 TARGET 的鏈接。
默認創建硬鏈接，符號鏈接使用 --symbolic。
默認情況下，每個目的地（新鏈接的名稱）不應該已經存在。
創建硬鏈接時，每個 TARGET 都必須存在。
符號鏈接可以包含任意文本；
如果稍後解析，相對鏈接將根據其父目錄進行解釋。
多頭期權的強制參數對於空頭期權也是強制性的。
ln
Debian / Ubuntu /
Raspberry Pi
$ man ln > ./man-docs/ln.md
$ cat ./man-docs/ln.md
-s, --symbolic
make symbolic links instead of hard links
$ man ln > ./man-docs/ln.md
$ cat ./man-docs/ln.md
make
symbolic links instead of hard linksLN(1) User Commands LN(1)
NAME
ln - make links between files
SYNOPSIS
ln [OPTION]... [-T] TARGET LINK_NAME
ln [OPTION]... TARGET
ln [OPTION]... TARGET... DIRECTORY
ln [OPTION]... -t DIRECTORY TARGET...
DESCRIPTION
In the 1st form, create a link to TARGET with the name LINK_NAME. In the 2nd form, create a link to TAR‐
GET in the current directory. In the 3rd and 4th forms, create links to each TARGET in DIRECTORY. Cre‐
ate hard links by default, symbolic links with --symbolic. By default, each destination (name of new
link) should not already exist. When creating hard links, each TARGET must exist. Symbolic links can
hold arbitrary text; if later resolved, a relative link is interpreted in relation to its parent direc‐
tory.
Mandatory arguments to long options are mandatory for short options too.
--backup[=CONTROL]
make a backup of each existing destination file
-b like --backup but does not accept an argument
-d, -F, --directory
allow the superuser to attempt to hard link directories (note: will probably fail due to system
restrictions, even for the superuser)
-f, --force
remove existing destination files
-i, --interactive
prompt whether to remove destinations
-L, --logical
dereference TARGETs that are symbolic links
-n, --no-dereference
treat LINK_NAME as a normal file if it is a symbolic link to a directory
-P, --physical
make hard links directly to symbolic links
-r, --relative
create symbolic links relative to link location
-s, --symbolic
make symbolic links instead of hard links
-S, --suffix=SUFFIX
override the usual backup suffix
-t, --target-directory=DIRECTORY
specify the DIRECTORY in which to create the links
-T, --no-target-directory
treat LINK_NAME as a normal file always
-v, --verbose
print name of each linked file
--help display this help and exit
--version
output version information and exit
The backup suffix is '~', unless set with --suffix or SIMPLE_BACKUP_SUFFIX. The version control method
may be selected via the --backup option or through the VERSION_CONTROL environment variable. Here are
the values:
none, off
never make backups (even if --backup is given)
numbered, t
make numbered backups
existing, nil
numbered if numbered backups exist, simple otherwise
simple, never
always make simple backups
Using -s ignores -L and -P. Otherwise, the last option specified controls behavior when a TARGET is a
symbolic link, defaulting to -P.
AUTHOR
Written by Mike Parker and David MacKenzie.
REPORTING BUGS
GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
Report any translation bugs to <https://translationproject.org/team/>
COPYRIGHT
Copyright © 2020 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later
<https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent
permitted by law.
SEE ALSO
link(2), symlink(2)
Full documentation <https://www.gnu.org/software/coreutils/ln>
or available locally via: info '(coreutils) ln invocation'
GNU coreutils 8.32 September 2020 LN(1)
macOS
$ man ln
$ man ln
LN(1) General Commands Manual LN(1)
NAME
ln, link – link files
SYNOPSIS
ln [-L | -P | -s [-F]] [-f | -iw] [-hnv] source_file [target_file]
ln [-L | -P | -s [-F]] [-f | -iw] [-hnv] source_file ... target_dir
link source_file target_file
DESCRIPTION
The ln utility creates a new directory entry (linked file) for the file
name specified by target_file. The target_file will be created with the
same file modes as the source_file. It is useful for maintaining
multiple copies of a file in many places at once without using up storage
for the “copies”; instead, a link “points” to the original copy. There
are two types of links; hard links and symbolic links. How a link
“points” to a file is one of the differences between a hard and symbolic
link.
The options are as follows:
-F If the target file already exists and is a directory, then remove
it so that the link may occur. The -F option should be used with
either -f or -i options. If neither -f nor -i is specified, -f is
implied. The -F option is a no-op unless -s is specified.
-L When creating a hard link to a symbolic link, create a hard link to
the target of the symbolic link. This is the default. This option
cancels the -P option.
-P When creating a hard link to a symbolic link, create a hard link to
the symbolic link itself. This option cancels the -L option.
-f If the target file already exists, then unlink it so that the link
may occur. (The -f option overrides any previous -i and -w
options.)
-h If the target_file or target_dir is a symbolic link, do not follow
it. This is most useful with the -f option, to replace a symlink
which may point to a directory.
-i Cause ln to write a prompt to standard error if the target file
exists. If the response from the standard input begins with the
character ‘y’ or ‘Y’, then unlink the target file so that the link
may occur. Otherwise, do not attempt the link. (The -i option
overrides any previous -f options.)
-n Same as -h, for compatibility with other ln implementations.
-s Create a symbolic link.
-v Cause ln to be verbose, showing files as they are processed.
-w Warn if the source of a symbolic link does not currently exist.
By default, ln makes hard links. A hard link to a file is
indistinguishable from the original directory entry; any changes to a
file are effectively independent of the name used to reference the file.
Directories may not be hardlinked, and hard links may not span file
systems.
A symbolic link contains the name of the file to which it is linked. The
referenced file is used when an open(2) operation is performed on the
link. A stat(2) on a symbolic link will return the linked-to file; an
lstat(2) must be done to obtain information about the link. The
readlink(2) call may be used to read the contents of a symbolic link.
Symbolic links may span file systems and may refer to directories.
Given one or two arguments, ln creates a link to an existing file
source_file. If target_file is given, the link has that name;
target_file may also be a directory in which to place the link; otherwise
it is placed in the current directory. If only the directory is
specified, the link will be made to the last component of source_file.
Given more than two arguments, ln makes links in target_dir to all the
named source files. The links made will have the same name as the files
being linked to.
When the utility is called as link, exactly two arguments must be
supplied, neither of which may specify a directory. No options may be
supplied in this simple mode of operation, which performs a link(2)
operation using the two passed arguments.
EXAMPLES
Create a symbolic link named /home/src and point it to /usr/src:
# ln -s /usr/src /home/src
Hard link /usr/local/bin/fooprog to file /usr/local/bin/fooprog-1.0:
# ln /usr/local/bin/fooprog-1.0 /usr/local/bin/fooprog
As an exercise, try the following commands:
# ls -i /bin/[
11553 /bin/[
# ls -i /bin/test
11553 /bin/test
Note that both files have the same inode; that is, /bin/[ is essentially
an alias for the test(1) command. This hard link exists so test(1) may
be invoked from shell scripts, for example, using the if [ ] construct.
In the next example, the second call to ln removes the original foo and
creates a replacement pointing to baz:
# mkdir bar baz
# ln -s bar foo
# ln -shf baz foo
Without the -h option, this would instead leave foo pointing to bar and
inside foo create a new symlink baz pointing to itself. This results
from directory-walking.
An easy rule to remember is that the argument order for ln is the same as
for cp(1): The first argument needs to exist, the second one is created.
COMPATIBILITY
The -h, -i, -n, -v and -w options are non-standard and their use in
scripts is not recommended. They are provided solely for compatibility
with other ln implementations.
The -F option is a FreeBSD extension and should not be used in portable
scripts.
SEE ALSO
link(2), lstat(2), readlink(2), stat(2), symlink(2), symlink(7)
STANDARDS
The ln utility conforms to IEEE Std 1003.2-1992 (“POSIX.2”).
The simplified link command conforms to Version 2 of the Single UNIX
Specification (“SUSv2”).
HISTORY
An ln command appeared in Version 1 AT&T UNIX.
macOS 13.4 May 10, 2021 macOS 13.4
demos
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