ln, link

Create additional pointers to a file

ln [-fhinsv] originalFile [newlink]
ln [-fhinsv] originalFile ... link_dir
link originalFile newlink

Creates a new directory entry resulting in multiple appearances of a file, perhaps in a different directory or to provide a consistant reference for new versions of a file.

By default creates a hard link. Cannot create a hard link if the newlink is on another volume or if originalFile is a directory. Then specify -s to create a symbolic link.
Both directory entries have the link count increased.


 > cd ~ 

        > ln ../yourdirectory/ournotes

notes

> ls -log docu ../yourdirectory/ournotes

        -rwxr-xr-x  2   20 Jan  5 11:43 ournotes 

        -rwxr-xr-x  2   20 Jan  5 11:43 ournotes

newlink may be a directory in which to place the new 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 link_dir to all the named source files. The links made will have the same name as the files being linked to.

`-i`	interactivey prompts standard error with:"`replace newlink?`" if `newlink` exists. A response from standard input begining with `y` unlinks ( deletes ) `newlink` then creates `newlink`. overrides any previous `-f`
`-f`	force creation if the newlink file already exists. overrides any previous `-i` .
`-v`	verbose, showing files as they are processed, as in `ln -v prefix*`
`-h,n`	If the `newlink_file` or `link_dir` is a symbolic link, do not follow it. Useful with `-f` to replace a symlink which may point to a directory.
`-s`	Create a symbolic link. ( no message is generated if original file does not exist! and return code is zero!)

link takes exactly two filenames and creates a hard link. No options may be supplied.

hard link vs symbolic link.

hard links, created by default, are file directory entries that contain a duplicate of the pointer to the originalFile and are indistinguishable from the original.
ls -l includes a link count of the number of directory entries which point to a file.
```
 
 > ./reptPgm >  origfile
 > ls -l origfile
-rw-r--r--  1 dgerman  devgrp  2419 Apr  9 13:50 origfile

 > ln origfile hardLink
 > ls -l orig* hard* 
-rw-r--r--  2 dgerman  devgrp  2419 Apr  9 13:50 origfile
-rw-r--r--  2 dgerman  devgrp  2419 Apr  9 13:50 hardlink
```
Changing the mode (permissions), owner, group … of one entry effects all entries.
removing a directory entry does not delete the file until the last entry is removed.
Hard links may referer to different directories but may not span file systems or volumes and may not refer to directories

Specify -s to create a symbolic directory link.

symbolic links add a file directory entry that contains contain the full path of the originalFile which is used if the entries exist on different volumes or refer to directories.
The originalFile is used when an open is performed on the symbolic link.
ls -l displays an l as the first character, unique date fields (these are part of the directory entry, not the file) and an "arrow" ( -> ) pointing to the originalFile. (additional date information is available using stat )
```
> ls -l *
lrwxr-xr-x  1 dgerman  devgrp  6 Apr  1 14:08 symlink -> target
-rw-r--r--  1 dgerman  devgrp  405 Apr  1 14:06 target
```
The link count for both entries may be 1 (if no hardlinks exist).
The size of a symbolic link is the number of characters in the originalFile full path name.
Changing the mode of the symbolic link actually effects the newlink !
There is no information in the target file that a symbolic link to it exists!
Unfortunately, removing the target file with out removing the synbolic link, causes accesses to the symbolic link to report: No such file or directory!
```
 
> ln -s "/Volumes/BACKUPS/notTimeMachine" mirror3
> ls -l mirror3
lrwxr-xr-x  dgerman  staff  33 Sep7 22:22 mirror3 -> /Volumes/BACKUPS/notTimeMachine
> ls -ld mirror3
lrwxr-xr-x  dgerman  staff  33 Sep7 22:22 mirror3 -> /Volumes/BACKUPS/notTimeMachine
> stat mirror3
234881028731036 lrwxr-xr-x dgerman (501) 0 33 
  "Sep7 22:22:34 2008" "Sep7 22:22:34 2008" "Sep7 22:22:34 2008" "Sep7 22:22:34 2008" 4096 8 0 mirror3
> readlink mirror3
/Volumes/BACKUPS/notTimeMachine
> cd mirror3
 mirror3 > 
```
Symbolic links may span file systems and may refer to directories.

stat on a symbolic link will return information about newlink.
stat -L displays information about the originalFile.
readlink is used to read the contents of a symbolic link and shows the path to the originalFile
See lstat,readlink,stat.

BUG: ln -s nofile newlink does not display a message if nofile does not exist and return code is set to 0!