Интерактивная система просмотра системных руководств (man-ов)
mutt_dotlock (1)
>> mutt_dotlock (1) ( Linux man: Команды и прикладные программы пользовательского уровня )
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
command line option) break a lock. The default value is 5.
mutt_dotlock
waits one second between successive locking attempts.
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
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.
