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link()                 COHERENT System Call                link()




Create a link

lliinnkk(_o_l_d, _n_e_w)
cchhaarr *_o_l_d, *_n_e_w;

A link to a file is another name for the file.  All attributes of
the file appear identical among all links.

link creates a link called new to an existing file named old.

For administrative  reasons, it is an error  for users other than
the superuser  to create a  link to a directory.   Such links can
make the  file system no longer  tree structured unless carefully
controlled, posing problems for commands such as find.

***** Example *****

This example, called lock.c, demonstrates how link can be used to
perform intertask  locking.  With  this technique, a  program can
start a  process in the  background and stop any  other user from
starting the identical process.


main()
{
        if(link("lock.c", "lockfile") == -1) {
                printf("Cannot link\n");
                exit(1);
        }



        sleep(50);      /* do nothing for 50 seconds */
        unlink("lockfile");
        printf("done\n");
        exit(0);
}


***** See Also *****

COHERENT system calls, find, ln, unlink()

***** Diagnostics *****

link  returns zero  when successful.   It  returns -1  on errors,
e.g., old  does not  exist, new  already exists, attempt  to link
across file systems, or no permission to create new in the target
directory.

***** Notes *****

Because  each mounted  file  system is  a self-contained  entity,
links between different mounted file systems fail.


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link()                 COHERENT System Call                link()




























































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