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/* ========================================================================
* Copyright 1988-2006 University of Washington
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
*
* ========================================================================
*/
/*
* Program: Exclusive create of a file, NFS kludge version
*
* Author: Mark Crispin
* Networks and Distributed Computing
* Computing & Communications
* University of Washington
* Administration Building, AG-44
* Seattle, WA 98195
* Internet: MRC@CAC.Washington.EDU
*
* Date: 17 December 1999
* Last Edited: 30 August 2006
*/
/* SUN-OS had an NFS, As kludgy as an albatross;
* And everywhere that it was installed, It was a total loss.
* -- MRC 9/25/91
*/
/* Exclusive create of a file
* Accepts: file name
* Return: T if success, NIL if failed, -1 if retry
*/
long crexcl (char *name)
{
long ret = -1;
int i;
char hitch[MAILTMPLEN];
struct stat sb;
int mask = umask (0);
/* build hitching post file name */
sprintf (hitch,"%s.%lu.%d.",name,(unsigned long) time (0),getpid ());
i = strlen (hitch); /* append local host name */
gethostname (hitch + i,(MAILTMPLEN - i) - 1);
/* try to get hitching-post file */
if ((i = open (hitch,O_WRONLY|O_CREAT|O_EXCL,(int) shlock_mode)) >= 0) {
close (i); /* close the hitching-post */
/* Note: link() may return an error even if it actually succeeded. So we
* always check for success via the link count, and ignore the error if
* the link count is right.
*/
/* tie hitching-post to lock */
i = link (hitch,name) ? errno : 0;
/* success if link count now 2 */
if (!stat (hitch,&sb) && (sb.st_nlink == 2)) ret = LONGT;
else if (i == EPERM) { /* links not allowed? */
/* Probably a FAT filesystem on Linux. It can't be NFS, so try creating
* the lock file directly.
*/
if ((i = open (name,O_WRONLY|O_CREAT|O_EXCL,(int) shlock_mode)) >= 0){
close (i); /* close the file */
ret = LONGT; /* success */
}
/* fail unless error is EEXIST */
else if (errno != EEXIST) ret = NIL;
}
unlink (hitch); /* flush hitching post */
}
/* fail unless error is EEXIST */
else if (errno != EEXIST) ret = NIL;
umask (mask); /* restore previous mask */
return ret;
}
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