1.\"- 2.\" Copyright (c) 1980, 1990, 1993 3.\" The Regents of the University of California. All rights reserved. 4.\" 5.\" This code is derived from software contributed to Berkeley by 6.\" the Institute of Electrical and Electronics Engineers, Inc. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)ln.1 8.2 (Berkeley) 12/30/93 33.\" $FreeBSD: head/bin/ln/ln.1 244791 2012-12-28 22:06:33Z gjb $ 34.\" 35.Dd March 23, 2015 36.Dt LN 1 37.Os 38.Sh NAME 39.Nm ln , 40.Nm link 41.Nd link files 42.Sh SYNOPSIS 43.Nm 44.Op Fl L | Fl P | Fl s Op Fl F 45.Op Fl f | iw 46.Op Fl hnv 47.Ar source_file 48.Op Ar target_file 49.Nm 50.Op Fl L | Fl P | Fl s Op Fl F 51.Op Fl f | iw 52.Op Fl hnv 53.Ar source_file ... 54.Ar target_dir 55.Nm link 56.Ar source_file Ar target_file 57.Sh DESCRIPTION 58The 59.Nm 60utility creates a new directory entry (linked file) for the file name 61specified by 62.Ar target_file . 63The 64.Ar target_file 65will be created with the same file modes as the 66.Ar source_file . 67It is useful for maintaining multiple copies of a file in many places 68at once without using up storage for the 69.Dq copies ; 70instead, a link 71.Dq points 72to the original copy. 73There are two types of links; hard links and symbolic links. 74How a link 75.Dq points 76to a file is one of the differences between a hard and symbolic link. 77.Pp 78The options are as follows: 79.Bl -tag -width flag 80.It Fl F 81If the target file already exists and is a directory, then remove it 82so that the link may occur. 83The 84.Fl F 85option should be used with either 86.Fl f 87or 88.Fl i 89options. 90If none is specified, 91.Fl f 92is implied. 93The 94.Fl F 95option is a no-op unless 96.Fl s 97option is specified. 98.It Fl L 99When creating a hard link to a symbolic link, 100create a hard link to the target of the symbolic link. 101This is the default. 102This option cancels the 103.Fl P 104option. 105.It Fl P 106When creating a hard link to a symbolic link, 107create a hard link to the symbolic link itself. 108This option cancels the 109.Fl L 110option. 111.It Fl f 112If the target file already exists, 113then unlink it so that the link may occur. 114(The 115.Fl f 116option overrides any previous 117.Fl i 118and 119.Fl w 120options.) 121.It Fl h 122If the 123.Ar target_file 124or 125.Ar target_dir 126is a symbolic link, do not follow it. 127This is most useful with the 128.Fl f 129option, to replace a symlink which may point to a directory. 130.It Fl i 131Cause 132.Nm 133to write a prompt to standard error if the target file exists. 134If the response from the standard input begins with the character 135.Sq Li y 136or 137.Sq Li Y , 138then unlink the target file so that the link may occur. 139Otherwise, do not attempt the link. 140(The 141.Fl i 142option overrides any previous 143.Fl f 144options.) 145.It Fl n 146Same as 147.Fl h , 148for compatibility with other 149.Nm 150implementations. 151.It Fl s 152Create a symbolic link. 153.It Fl v 154Cause 155.Nm 156to be verbose, showing files as they are processed. 157.It Fl w 158Warn if the source of a symbolic link does not currently exist. 159.El 160.Pp 161By default, 162.Nm 163makes 164.Em hard 165links. 166A hard link to a file is indistinguishable from the original directory entry; 167any changes to a file are effectively independent of the name used to reference 168the file. 169Directories may not be hardlinked, and hard links may not span file systems. 170.Pp 171A symbolic link contains the name of the file to 172which it is linked. 173The referenced file is used when an 174.Xr open 2 175operation is performed on the link. 176A 177.Xr stat 2 178on a symbolic link will return the linked-to file; an 179.Xr lstat 2 180must be done to obtain information about the link. 181The 182.Xr readlink 2 183call may be used to read the contents of a symbolic link. 184Symbolic links may span file systems and may refer to directories. 185.Pp 186Given one or two arguments, 187.Nm 188creates a link to an existing file 189.Ar source_file . 190If 191.Ar target_file 192is given, the link has that name; 193.Ar target_file 194may also be a directory in which to place the link; 195otherwise it is placed in the current directory. 196If only the directory is specified, the link will be made 197to the last component of 198.Ar source_file . 199.Pp 200Given more than two arguments, 201.Nm 202makes links in 203.Ar target_dir 204to all the named source files. 205The links made will have the same name as the files being linked to. 206.Pp 207When the utility is called as 208.Nm link , 209exactly two arguments must be supplied, 210neither of which may specify a directory. 211No options may be supplied in this simple mode of operation, 212which performs a 213.Xr link 2 214operation using the two passed arguments. 215.Sh VARIANT SYMLINKS 216.Dx 217supports a special kind of dynamic 218symbolic link called a 219.Em variant symlink . 220The 221.Ar source_file 222of a variant symlink may contain one or more variable names. 223Each of these variable names is enclosed in braces and preceded by a 224dollar sign in the style of variable references in 225.Xr sh 1 226and 227.Xr csh 1 . 228.Pp 229Whenever a variant symlink is followed, each variable found in 230.Ar source_file 231is replaced by its associated value. 232In this manner, a variant symlink may resolve to different 233paths based on context. 234The facility supports per-process, per-user, and system-wide varsyms. 235.Pp 236Varsym variables can be set with the 237.Xr varsym 1 238utility. 239Regular 240.Xr environ 7 241environment variables are not used to resolve variant symlinks. 242.Sh EXAMPLES 243Create a symbolic link named 244.Pa /home/src 245and point it to 246.Pa /usr/src : 247.Pp 248.Dl # ln -s /usr/src /home/src 249.Pp 250Hard link 251.Pa /usr/local/bin/fooprog 252to file 253.Pa /usr/local/bin/fooprog-1.0 : 254.Pp 255.Dl # ln /usr/local/bin/fooprog-1.0 /usr/local/bin/fooprog 256.Pp 257As an exercise, try the following commands: 258.Bd -literal -offset indent 259# ls -i /bin/[ 26011553 /bin/[ 261# ls -i /bin/test 26211553 /bin/test 263.Ed 264.Pp 265Note that both files have the same inode; that is, 266.Pa /bin/[ 267is essentially an alias for the 268.Xr test 1 269command. 270This hard link exists so 271.Xr test 1 272may be invoked from shell scripts, for example, using the 273.Li "if [ ]" 274construct. 275.Pp 276In the next example, the second call to 277.Nm 278removes the original 279.Pa foo 280and creates a replacement pointing to 281.Pa baz : 282.Bd -literal -offset indent 283# mkdir bar baz 284# ln -s bar foo 285# ln -shf baz foo 286.Ed 287.Pp 288Without the 289.Fl h 290option, this would instead leave 291.Pa foo 292pointing to 293.Pa bar 294and inside 295.Pa foo 296create a new symlink 297.Pa baz 298pointing to itself. 299This results from directory-walking. 300.Pp 301An easy rule to remember is that the argument order for 302.Nm 303is the same as for 304.Xr cp 1 : 305The first argument needs to exist, the second one is created. 306.Pp 307A simple variable symlink example: 308.Bd -literal -offset indent 309sysctl vfs.varsym_enable=1 310 311ln -s 'a${fubar}b' test 312 313echo 'Hello' > axxb 314echo 'Goodbye' > ayyb 315 316varsym fubar=xx; cat test 317varsym fubar=yy; cat test 318.Ed 319.Sh COMPATIBILITY 320The 321.Fl h , 322.Fl i , 323.Fl n , 324.Fl v 325and 326.Fl w 327options are non-standard and their use in scripts is not recommended. 328They are provided solely for compatibility with other 329.Nm 330implementations. 331.Pp 332Variant symlinks are unique (among BSDs) to 333.Dx . 334.Pp 335The 336.Fl F 337option is a 338.Fx 339extension and should not be used in portable scripts. 340.Sh SEE ALSO 341.Xr varsym 1 , 342.Xr link 2 , 343.Xr lstat 2 , 344.Xr readlink 2 , 345.Xr stat 2 , 346.Xr symlink 2 , 347.Xr symlink 7 348.Sh STANDARDS 349The 350.Nm 351utility conforms to 352.St -p1003.2-92 . 353.Pp 354The simplified 355.Nm link 356command conforms to 357.St -susv2 . 358.Sh HISTORY 359An 360.Nm 361command appeared in 362.At v1 . 363