Re: Re: Problem with database engine on Cygwin

[günter strubinsky <strubinsky at cox dot net>]

Just to follow the 20 char filename and the chnces it might appear to become a real filename, if you prepend the generated fn with, let's s 5 underscores your chnaces that this filename will ever exist are NIL!

I have never seen files with a name like that over the last 20 years.

It does not fix the original problem but keeps Murphy out of all!

guenter
> 
> From: dmay at tvi dot edu
> Date: 2003/04/09 Wed PM 03:49:50 EDT
> To: lhall at rfk dot com
> CC: cygwin at cygwin dot com
> Subject: Re: Problem with database engine on Cygwin
> 
> On  9 Apr, lhall at pop dot ma dot ultranet dot com wrote: 
> | Hi David,
> | 
> | The semantics of deleting a file on UNIX/Linux systems is different than
> | on Windows with the Win32 API.  Traditionally, access issues during deletion
> | under Cygwin could cause the unlink call to succeed in some circumstances 
> | (the file was open by some other application requesting exclusivity) even 
> | if the file was not immediately deleted.  There has been more work in this
> | area recently as Chris Faylor pointed out.  But you may need to dig deeper
> | than the POSIX API boundary to get a better understanding of the problem 
> | you're seeing, though looking at the return values may give some clue.
> | Sounds like Igor Pechtchanski is already looking at the unlink() code in 
> | cygwin1.dll for his problem.  Perhaps he'll turn up something that will 
> | help you too.
> | 
> | Larry
> | 
> | 
> | 
> | 
> | --------------------------------------------------------------------
> | mail2web - Check your email from the web at
> | http://mail2web.com/ .
> | 
> | 
> OK.  I devised a work-around.  You are probably right that the problem occurs
> when you try to delete the file.  Apparently, the system still has some sense
> that the file is still there, even though it is not.  The error condition is
> definitely occuring at the point that I try to create a file with the same
> name that has been deleted. There is a small C file attached that compiles
> cleanly under Cygwin that shows the behavior I am seeing with my database
> engine. Basically, as you can see when you run this code, on the second call
> to creat(), you get a permission denied error. Is this a windows thing or is
> it a cygwin thing?  I don't have VC++, so I can't compile this for pure
> windows and see how it works.  Would someone who has VC++ please do that for
> my curiosity and let me know what the result is?  You will have to change the
> code slightly if you do.
> 
> I worked around the issue in my code by closing the offending file, renaming
> it to a 20 character pseudo-random string and then deleting it.  When I did
> that, I had no problem creating another file with the same name.  The problem
> here is if I happen to get 2 20-character psuedo-random strings that are
> identical (not likely, I know), this is going to fail.
> 
> So, I kludged it in a somewhat unclean, albeit functional, way.  Is there
> another workaround that is a little more elegant?
> 
> Thanks again for the responses so far...I am interested in the final
> disposition of this issue although I don't lurk the list.
> -- 
> =================================
> David May
> Senior UNIX System Administrator
> Albuquerque TVI
> 505-224-3015
> #include <sys/types.h>
> #include <sys/stat.h>
> #include <fcntl.h>
> 
> #include <sys/errno.h>
> 
> #include <stdio.h>
> #include <stdlib.h>
> #include <unistd.h>
> 
> char buf[] = "abcdefghijkABCDEFGHIJK";
> #define	FILENAME	"test_windows_file"
> 
> int main (void)
> {
> 	int fd;
> 	int status;
> 
> 	fd = creat (FILENAME, (S_IWRITE|S_IREAD));
> 	if (-1 == fd)	{
> 		printf ("\n\nError creating %s:\n", FILENAME);
> 		perror(0);
> 		return -1;
> 	}
> #ifdef __CYGWIN__
> 	fd = open (FILENAME, (O_RDWR|O_BINARY), (S_IREAD|S_IWRITE));
> #endif
> #ifndef __CYGWIN__
> 	fd = open (FILENAME, O_RDWR, (S_IREAD|S_IWRITE));
> #endif
> 	if (-1 == fd)	{
> 		printf ("\n\nError opening %s:\n", FILENAME);
> 		perror(0);
> 		return -1;
> 	}
> 	status = write (fd, buf, 20);
> 	if (status != 20)	{
> 		printf ("\n\nError writing to %s\n", FILENAME);
> 		return -1;
> 	}
> 	status = close (fd);
> 	if (0 != status)	{
> 		printf ("\n\nError closing %s\n", FILENAME);
> 		return -1;
> 	}
> 	status = remove (FILENAME);
> 	if (-1 == status)	{
> 		printf ("\n\nError removing %s\n", FILENAME);
> 		return -1;
> 	}
> 	fd = 0;
> 	fd = creat (FILENAME, (S_IWRITE|S_IREAD));
> 	if (-1 == fd)	{
> 		printf ("\n\nError creating %s again:\n", FILENAME);
> 		perror(0);
> 		return -1;
> 	}
> 	fd = open (FILENAME, (O_RDWR|O_BINARY), (S_IREAD|S_IWRITE));
> 	if (-1 == fd)	{
> 		printf ("\n\nError opening %s:\n", FILENAME);
> 		perror(0);
> 		return -1;
> 	}
> 	status = write (fd, buf, 20);
> 	if (status != 20)	{
> 		printf ("\n\nError writing to %s\n", FILENAME);
> 		return -1;
> 	}
> 	status = write (fd, "\n", 1);
> 	if (status != 1)	{
> 		printf ("\n\nError writing to %s\n", FILENAME);
> 		return -1;
> 	}
> 	status = write (fd, buf, 20);
> 	if (status != 20)	{
> 		printf ("\n\nError writing to %s\n", FILENAME);
> 		return -1;
> 	}
> 	status = close (fd);
> 	if (0 != status)	{
> 		printf ("\n\nError closing %s again\n", FILENAME);
> 		return -1;
> 	}
> 	return 0;
> }
> 
> 
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