dotlock(1)			 User Manuals			    dotlock(1)



NAME
       mutt_dotlock - Lock mail spool files.

SYNOPSIS
       mutt_dotlock [-t|-f|-u|-d] [-p] [-r retries] file

DESCRIPTION
       mutt_dotlock implements the traditional mail spool file locking method:
       To lock file, a file named file.lock is created. The  program  operates
       with group mail privileges if necessary.

OPTIONS
       -t     Just  try.   mutt_dotlock wont actually lock a file, but inform
	      the invoking process if its at all possible to lock file.

       -f     Force the lock.  If another process holds a lock on file	longer
	      than a certain amount of time, mutt_dotlock will break that lock
	      by removing the lockfile.

       -u     Unlock.  mutt_dotlock will remove file.lock.

       -d     Delete.  mutt_dotlock will lock file, remove it if it has length
	      0, and afterwards remove file.lock.

       -p     Use privileges.  If given this option, mutt_dotlock will operate
	      with group mail  privileges  when  creating  and	deleting  lock
	      files.

       -r retries
	      This  command  line  option  tells  mutt_dotlock	to try locking
	      retries times before giving up or (if invoked with the  -f  com
	      mand  line  option)  break  a  lock.   The  default  value is 5.
	      mutt_dotlock  waits  one	second	between   successive   locking
	      attempts.

FILES
       file.lock
	      The lock file mutt_dotlock generates.

SEE ALSO
       fcntl(2), flock(2), lockfile(1), mutt(1)

DIAGNOSTICS
       mutt_dotlock gives all diagnostics in its return values:

       0 - DL_EX_OK
	      The program was successful.

       1 - DL_EX_ERROR
	      An  unspecified  error such as bad command line parameters, lack
	      of system memory and the like has occured.

       3 - DL_EX_EXIST
	      The user wants to lock a file which has been locked  by  another
	      process already.	If mutt_dotlock is invoked with the -f command
	      line option, mutt_dotlock wont generate this error,  but	break
	      other processes locks.

       4 - DL_EX_NEED_RPIVS
	      This  return  value only occurs if mutt_dotlock has been invoked
	      with the -t command line option.	 It  means  that  mutt_dotlock
	      will have to use its group mail privileges to lock file.

       5 - DL_EX_IMPOSSIBLE
	      This  return  value only occurs if mutt_dotlock has been invoked
	      with the -t command line option.	It means that mutt_dotlock  is
	      unable to lock file even with group mail privileges.

NOTES
       mutt_dotlock tries to implement an NFS-safe dotlocking method which was
       borrowed from lockfile (1).

       If the user cant open file for reading  with  his  normal  privileges,
       mutt_dotlock  will  return  the DL_EX_ERROR exit value to avoid certain
       attacks against other users spool files.  The  code  carefully  avoids
       race  conditions when checking permissions; for details of all this see
       the comments in dotlock.c.

HISTORY
       mutt_dotlock is part of the Mutt mail user agent package.  It has  been
       created to avoid running mutt with group mail privileges.

AUTHOR
       Thomas Roessler 



Unix				  AUGUST 1999			    dotlock(1)