mutt_dotlock(1)



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 won't actually lock a file, but inform
              the invoking process if it's 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 occurred.

       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 won't 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 can't 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 <roessler@does-not-exist.org>

Unix                              AUGUST 1999                       dotlock(1)

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