HardLinks and Softlinks Post: 302556440

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Top Forums Shell Programming and Scripting HardLinks and Softlinks Post 302556440 by ahmad.diab on Sunday 18th of September 2011 02:17:00 PM

09-18-2011

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you can control the permission by using "chmod" command , to create a soft link use "ln -s" command

---------- Post updated at 21:17 ---------- Previous update was at 21:15 ----------

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Creating Hard and Symbolic Links
To create a symbolic link or a hard link, you use the same command name, In, which has the following syntax:

In [-fns] <source> [<target>]


Hard link is the default output of the ln command-that is, if you issue the ln command without the - s option, a hard link will be created.
 

In this command, <source> is the original file and <target> is the link that will be created and linked to the <source>. The options for the command are listed here:

-f (force). Link the file without questioning the user.

-n. If the <target> is an existing file, do not overwrite the content of the file. The -f option overrides this option.

-s. Create a symbolic link. The default is a hard link.

The hard links and symbolic links are compared in Table 4-2 

Table 4-2: Comparison of hard and soft links  Characteristic
 Hard Link
 Soft Link
 
Existence of original file
 You cannot create a hard link to a file that does not exist.
 You can create a symbolic link to a file that does not exist.
 
File systems
 A hard link cannot span file systems-that is, the link and the file it points to have to be in the same file system.
 A soft link can span file systems.
 
Kind of original file
 A hard link can only point to a file that is not a directory.
 A soft link can point to a file or a directory.
 
I-node
 A hard link has the same inode number as the file it points to.
 A soft link has a different inode from the file it points to.

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symlink

symlink(4)						     Kernel Interfaces Manual							symlink(4)

NAME

       symlink - symbolic link

DESCRIPTION

       A symbolic (or soft ) link is a file whose name indirectly refers (points) to a relative or absolute path name.

       During  path  name  interpretation,  a symbolic link to a relative path name is expanded to the path name being interpreted, and a symbolic
       link to an absolute path name is replaced with the path name being interpreted.

       Thus, given the path name

	      If is a symbolic link to a relative path name such as the path name is interpreted as

	      If is a symbolic link to an absolute path name such as the path name is interpreted as

       All symbolic links are interpreted in this manner, with one exception: when the symbolic link is the last component of a path name,  it	is
       passed  as  a  parameter  to  one of the system calls: or (see readlink(2), rename(2), symlink(2), unlink(2), chown(2) and lstat(2)).  With
       these calls, the symbolic link, itself, is accessed or affected.

       Unlike normal (hard) links, a symbolic link can refer to any arbitrary path name and can span different logical devices (volumes).

       The path name can be that of any type of file (including a directory or another symbolic link), and may be invalid if no such  path  exists
       in  the	system.   (It is possible to make symbolic links point to themselves or other symbolic links in such a way that they form a closed
       loop.  The system detects this situation by limiting the number of symbolic links it traverses while translating a path name.)

       The mode and ownership of a symbolic link is ignored by the system, which means that affects the actual file, but not the  file	containing
       the symbolic link (see chmod(1)).

       Symbolic links can be created using or (see ln(1) and symlink(2)).

AUTHOR

       was developed by HP and the University of California, Berkeley.

SEE ALSO

       cp(1), symlink(2), readlink(2), link(2), stat(2), mknod(1M).

																	symlink(4)