Edward Roper wrote:
> Okay I'm still lost. :)
>
> What type of filelocking should be used when dealing with mailboxes. Does
> Sendmail honor a particular "lock file" or do I use flock() or fcntl()?
sendmail doesn't touch mail spools; it invokes an MDA such as
procmail, deliver, mail.local etc to deliver mail.
The standard way to lock a mailbox is to create a file whose name is
that of the mailbox with `.lock' appended. The main subtlety is that
you have to create it with link(), as this is the only approach that
is guaranteed to be atomic on an NFS filesystem.
IOW:
int lock_file(const char *name)
{
size_t n = strlen(name);
char *buff1 = alloca(n + 6);
char *buff2 = alloca(n + 6);
int fd;
sprintf(buff1, "%s.%04x", name, getpid());
fd = open(buff1, O_WRONLY | O_CREAT | O_EXCL, 0);
if (fd < 0)
{
perror("lock_file: open");
return -1;
}
if (close(fd) < 0)
{
perror("lock_file: close");
return -1;
}
sprintf(buff2, "%s.lock", name);
if (link(buff1, buff2) < 0)
{
if (errno != EEXIST)
{
perror("lock_file: link");
status = -1;
}
else
status = 0;
}
else
status = 1;
if (unlink(buff1) < 0)
perror("lock_file: unlink");
return status;
}
The function returns 1 if the file was locked successfully, 0 if the
file was already locked, and -1 if an error occurred.
--
Glynn Clements <[EMAIL PROTECTED]>
