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'''<code>ln</code>''' is the Linux command for creating a link to a file or folder.
'''<code>ln</code>''' is the Linux command for creating a link to a file or folder.


To create a relative link:
This page so far only discusses ''symbolic'' links, not ''hard'' links. (TODO)
  ln -r --symbolic {{arg|existing file}} {{arg|link to create}}
==General Syntax==
* Relative links will still work even if the folder containing both files (the original and the link) is moved or copied.
ln {{fmt/opt|-r}} --symbolic {{arg|filespec of existing file/folder}} {{arg|filespec for new link}}
* Note that a link cannot have the same name as a folder in the same directory.
===scenarios===
* If you're in the folder '''where you want the link to be created''':
  ln {{fmt/opt|-r}} --symbolic {{arg|path to existing file/folder}} ./{{arg|name for new link}}
* If you're in the folder '''where the existing/real file is''':
ln {{fmt/opt|-r}} --symbolic ./{{arg|name of existing file}} {{arg|path to new link}}
===notes===
* A link cannot have the same name as a folder in the same directory (same rule as if it were a regular file).
* The <code>-r</code> option just tells <code>ln</code> to ''calculate'' the relative path from the link to the existing file, and ''use that'' as the link URL; see "Relative Links" below.
==Errors==
* The error message "ln: failed to create symbolic link '{{arg|filename}}': File exists" can be maddeningly misleading. It seems to always report the existing file, even when the problem is actually that the ''second'' filename (the link-name) already exists. Translation:
* The error message "ln: failed to create symbolic link '{{arg|filename}}': File exists" can be maddeningly misleading. It seems to always report the existing file, even when the problem is actually that the ''second'' filename (the link-name) already exists. Translation:
** "<tt>'{{arg|arg 1}}': File exists</tt>" (arg 1 should be {{arg|existing file}}): The link-name is the same as an existing file, possibly a folder.
** "<tt>'{{arg|arg 1}}': File exists</tt>" (arg 1 should be {{arg|existing file}}): The link-name is the same as an existing file, possibly a folder.
*** The fact that <code>ln</code> reports the first param instead of the second one seems to be a {{l/sub|bug}}. Yes, the first param is a file that does exist, but that's not the problem.
*** The fact that <code>ln</code> reports the first param instead of the second one seems to be a {{l/sub|bug}}. Yes, the first param is a file that does exist, but that's not the problem.
** "<tt>'{{arg|arg 2}}': File exists</tt>" (arg 2 should be {{arg|name for link}}): You've got the arguments backwards, and are trying to create a link under the same name as the existing file (to a file which doesn't exist).
** "<tt>'{{arg|arg 2}}': File exists</tt>" (arg 2 should be {{arg|name for link}}): You've got the arguments backwards, and are trying to create a link under the same name as the existing file (to a file which doesn't exist).
===another way to think of it===
==Relative Links==
If you're in the folder '''where you want the link to go''':
Note that when <code>ln</code> creates a relative link using the <code>-r</code> option, all it is doing is calculating the relative path for you and then using that as the link's target-string (URL). You can create a relative link without <code>-r</code> by just specifying a relative path. There's no difference between an absolute link and a relative link except whether the URL uses any relative-path syntax (e.g. "../", or no initial "/").
ln -r --symbolic {{arg|relative path}}/{{arg|name of file/folder}} ./{{arg|name for link}}


If you're in the folder '''where the existing/real file is''':
Relative links will still work even if the folder containing both files (the original and the link) is moved or copied, which can be useful for making links within a portable code repository. ([[Git]] does store link-files by default.)
ln -r --symbolic ./{{arg|name of file}} {{arg|relative path}}/{{arg|name for link}}
==Example==
I pretty much always get confused as to which is the link and which is the target, so here's an example. You're inside {{fmt/code|/git/futilities/human/ff}} and you want to create a link called "lib" to the "lib" folder at {{fmt/code|/git/futilities/lib}}:
ln -r --symbolic ../../lib/ ./lib
==Notes==
==Notes==
* [http://stackoverflow.com/questions/1347105/linux-link-all-files-from-one-to-another-directory LINUX: Link all files from one to another directory]
* [http://stackoverflow.com/questions/1347105/linux-link-all-files-from-one-to-another-directory LINUX: Link all files from one to another directory]

Revision as of 22:19, 11 December 2024

ln is the Linux command for creating a link to a file or folder.

This page so far only discusses symbolic links, not hard links. (TODO)

General Syntax

ln Template:Fmt/opt --symbolic Template:Arg Template:Arg

scenarios

  • If you're in the folder where you want the link to be created:
ln Template:Fmt/opt --symbolic Template:Arg ./Template:Arg
  • If you're in the folder where the existing/real file is:
ln Template:Fmt/opt --symbolic ./Template:Arg Template:Arg

notes

  • A link cannot have the same name as a folder in the same directory (same rule as if it were a regular file).
  • The -r option just tells ln to calculate the relative path from the link to the existing file, and use that as the link URL; see "Relative Links" below.

Errors

  • The error message "ln: failed to create symbolic link 'Template:Arg': File exists" can be maddeningly misleading. It seems to always report the existing file, even when the problem is actually that the second filename (the link-name) already exists. Translation:
    • "'Template:Arg': File exists" (arg 1 should be Template:Arg): The link-name is the same as an existing file, possibly a folder.
      • The fact that ln reports the first param instead of the second one seems to be a Template:L/sub. Yes, the first param is a file that does exist, but that's not the problem.
    • "'Template:Arg': File exists" (arg 2 should be Template:Arg): You've got the arguments backwards, and are trying to create a link under the same name as the existing file (to a file which doesn't exist).

Note that when ln creates a relative link using the -r option, all it is doing is calculating the relative path for you and then using that as the link's target-string (URL). You can create a relative link without -r by just specifying a relative path. There's no difference between an absolute link and a relative link except whether the URL uses any relative-path syntax (e.g. "../", or no initial "/").

Relative links will still work even if the folder containing both files (the original and the link) is moved or copied, which can be useful for making links within a portable code repository. (Git does store link-files by default.)

Notes

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