ln [OPTION] SRC DEST
!subtitle:功能
创建文件的硬链接或软链接（符号链接）。
!subtitle:类型
可执行文件（/usr/bin/ln），属于 coreutils。
!subtitle:参数
OPTION 选项：
--backup[=CONTROL] - 选择怎样备份被覆盖的目标文件
-b - 备份被覆盖的目标文件
-d, -F, --directory - 允许超级用户尝试创建目录的硬链接
-f, --force - 强制操作，目标存在且无法打开时会尝试将其删除
-i, --interactive - 覆盖前提示
-L, --logical - 源文件是符号链接时，链接该链接的源文件，而不是该链接自身
-n, --no-dereference - 目标是指向目录的符号链接时将其视作普通文件进行覆盖
-P, --physical - 源文件是符号链接时，直接创建指向该链接的硬链接
-r, --relative - 将源文件的路径转换为参照符号链接所在目录的相对路径（与 -s 一起使用）
-s, --symbolic - 创建符号链接，而不是硬链接
-S, --suffix=SUFFIX - 使用 SUFFIX 作为备份文件的后缀；默认后缀为 ~
-t, --target-directory=DIRECTORY - 指定要创建链接的目录
-T, --no-target-directory - 将 DEST 视为文件（如果 DEST 是目录，则进行覆盖而非复制到它内部）
-v, --verbose - 打印详细信息
--help - 显示帮助
--version - 显示版本
SRC - 源文件
DEST - 目标文件（硬链接）
!subtitle:绝对路径
$ ln -s /opt/xxxx/cmd /usr/bin/ # 将 /opt/xxxx/cmd 链接到 /usr/bin/cmd
$ ls -l /usr/bin/cmd
lrwx-wxr-x 1 root root 5 Nov 17 12:12 /usr/bin/cmd -> /opt/xxxx/cmd
/usr/bin/cmd 是链接到 /opt/xxxx/cmd 的软连接
!subtitle:相对路径
$ ln -sr ./cmd ./dir # 将 ./cmd 链接到 ./dir/cmd
$ ls -l ./dir/cmd
lrwx-wxr-x 1 root root 5 Nov 17 12:12 ./dir/cmd -> ../cmd
./dir/cmd 是链接到 ../cmd 的软连接
$ ln -s ./cmd ./dir # 将 ./cmd 链接到 ./dir/cmd
$ ls -l ./dir/cmd
lrwx-wxr-x 1 root root 5 Nov 17 12:12 ./dir/cmd -> ./cmd
./dir/cmd 是链接到 ./cmd 的软连接
软连接在解析时相对路径参照自身所在目录，因此无法找到源文件，./cmd 指向自身导致无限递归错误。
| 命令 | 说明 |
|---|---|
| link | 创建文件的硬链接 |
| readlink | 获取符号链接的源文件 |
LN(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 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.
--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 su‐
peruser)
-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
with -s, create 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 SIM‐
PLE_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 con‐
trols 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 © 2023 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 9.4 April 2024 LN(1)