From: "Ara.T.Howard" <Ara.T.Howard@...>
Date: 2005-06-13T03:40:30+09:00
Subject: Re: File.link() error message

On Sun, 12 Jun 2005, a slow loris wrote:

> Why does File.link() report that the source file exists? It really
> ought to only report that the destination file exists. It isn't an
> error for the source to exist. If it didn't, we'd get ENOENT, not
> EEXIST.

ENOENT is returned only if

   harp:~ > man 2 link
   ...
   ...
   SYNOPSIS
          #include <unistd.h>

          int link(const char *oldpath, const char *newpath);

   ...
   ...

          ENOENT A directory component in oldpath or newpath does not  exist  or
                        is a dangling symbolic link.


otherwise ENOEXIST is returned as this shows

   harp:~ > cat a.c
   #include <stdlib.h>
   #include <stdio.h>
   #include <string.h>
   #include <errno.h>
   #include <unistd.h>
   main (int argc, char **argv)
   {
       char command[256];
         link (argv[1], argv[2]);
           sprintf (command, "ruby -e'p(SystemCallError::new(%d))'", errno);
             system(command);
   }

   harp:~ > gcc a.c

   harp:~ > ls foo
   ls: foo: No such file or directory

   harp:~ > ls bar
   ls: bar: No such file or directory

   harp:~ > a.out foo bar
   #<Errno::ENOENT: No such file or directory>


ENOENT is returned if we are dealing with bad directories only

   harp:~ > a.out /no/such/path/foo bar
   #<Errno::ENOENT: No such file or directory>

   harp:~ > a.out foo /no/such/path/bar
   #<Errno::ENOENT: No such file or directory>

but two good dirs always result in ENOEXIST

   harp:~ > a.out /usr/foo /usr/bar
   #<Errno::ENOENT: No such file or directory>

and a subsequent stat to determine which pathname did not exist would be a
race condition so i think you are stuck with this.

cheers.

-a
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