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31 .\" @(#)ln.1 8.2 (Berkeley) 12/30/93
32 .\" $FreeBSD: src/bin/ln/ln.1,v 1.11.2.8 2003/02/04 07:31:59 keramida Exp $
33 .\" $DragonFly: src/bin/ln/ln.1,v 1.8 2008/09/07 07:54:48 swildner Exp $
35 .Dd September 27, 2009
52 .Ar source_file Ar target_file
56 utility creates a new directory entry (linked file) which has the
57 same modes as the original file.
58 It is useful for maintaining multiple copies of a file in many places
59 at once without using up storage for the
64 There are two types of links; hard links and symbolic links.
67 to a file is one of the differences between a hard and symbolic link.
69 The options are as follows:
72 If the target file already exists,
73 then unlink it so that the link may occur.
76 option overrides any previous
84 is a symbolic link, do not follow it.
85 This is most useful with the
87 option, to replace a symlink which may point to a directory.
91 to write a prompt to standard error if the target file exists.
92 If the response from the standard input begins with the character
96 then unlink the target file so that the link may occur.
97 Otherwise, do not attempt the link.
100 option overrides any previous
106 for compatibility with other
110 Create a symbolic link.
114 to be verbose, showing files as they are processed.
122 A hard link to a file is indistinguishable from the original directory entry;
123 any changes to a file are effectively independent of the name used to reference
125 Hard links may not normally refer to directories and may not span file systems.
127 A symbolic link contains the name of the file to which it is linked.
128 The referenced file is used when an
130 operation is performed on the link.
133 on a symbolic link will return the linked-to file; an
135 must be done to obtain information about the link.
138 call may be used to read the contents of a symbolic link.
139 Symbolic links may span file systems and may refer to directories.
141 Given one or two arguments,
143 creates a link to an existing file
147 is given, the link has that name;
149 may also be a directory in which to place the link;
150 otherwise it is placed in the current directory.
151 If only the directory is specified, the link will be made
152 to the last component of
155 Given more than two arguments,
159 to all the named source files.
160 The links made will have the same name as the files being linked to.
162 When the utility is called as
164 exactly two arguments must be supplied,
165 neither of which may specify a directory.
166 No options may be supplied in this simple mode of operation,
169 operation using the two passed arguments.
172 supports a special kind of dynamic
173 symbolic link called a
174 .Em variant symlink .
177 of a variant symlink may contain one or more variable names.
178 Each of these variable names is enclosed in braces and preceded by a
179 dollar sign in the style of variable references in
184 Whenever a variant symlink is followed, each variable found in
186 is replaced by its associated value.
187 In this manner, a variant symlink may resolve to different
188 paths based on context.
189 The facility supports per-process, per-user, and system-wide varsyms.
191 Varsym variables can be set with the
196 environment variables are not used to resolve variant symlinks.
198 .Bd -literal -offset indent
199 sysctl vfs.varsym_enable=1
201 ln -s 'a${fubar}b' test
204 echo 'Goodbye' > ayyb
206 varsym fubar=xx; cat test
207 varsym fubar=yy; cat test
216 options are non-standard and their use in scripts is not recommended.
217 They are provided solely for compatibility with other
221 Variant symlinks are unique (among BSDs) to