mailunlock man page on SmartOS

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       maillock,  mailunlock,  touchlock - functions to manage lockfile(s) for
       user's mailbox

       cc [ flag ... ] file ... -lmail [ library ... ]
       #include <maillock.h>

       int maillock(const char *user, int retrycnt);

       void mailunlock(void);

       void touchlock(void);

       The maillock() function attempts to create a lockfile  for  the	user's
       mailfile. If a lockfile already exists, and it has not been modified in
       the last 5 minutes, maillock() will remove the lockfile and set its own

       It  is crucial that programs locking mail files refresh their locks  at
       least every three minutes to maintain the lock. Refresh the lockfile by
       calling the touchlock() function with no arguments.

       The  algorithm  used  to	 determine  the age of the lockfile takes into
       account clock drift between machines using a  network  file  system.  A
       zero  is	 written into the lockfile so that the lock will  be respected
       by systems running the standard version of System V.

       If the lockfile has been modified in the last 5	minutes	  the  process
       will sleep until the lock is available. The sleep algorithm is to sleep
       for 5 seconds times the attempt number. That is, the first  sleep  will
       be for 5 seconds, the next sleep will be for 10 seconds, etc. until the
       number of attempts reaches retrycnt.

       When the lockfile is no longer needed, it should be removed by  calling

       The  user  argument is the login name of the user for whose mailbox the
       lockfile will be created. maillock() assumes that user's mailfiles  are
       in the ``standard'' place as defined in	<maillock.h>.

       Upon successful completion, .maillock() returns 0. Otherwise it returns

			   user mailbox files

			   user mailbox lockfiles

       See attributes(5) for descriptions of the following attributes:

       │MT-Level       │ Unsafe		 │


       The mailunlock() function will only remove the  lockfile	 created  from
       the  most previous call to maillock(). Calling maillock() for different
       users without intervening calls to mailunlock()	will  cause  the  ini‐
       tially  created	lockfile(s) to remain, potentially blocking subsequent
       message delivery until the current process finally terminates.

				 Mar 29, 1999		       MAILLOCK(3MAIL)

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