NAME¶
lbdb_dotlock - Lock mail spool files.
SYNOPSIS¶
lbdb_dotlock [-t|-f|-u|-d] [-r
retries]
file
DESCRIPTION¶
dotlock implements the traditional mail spool file locking method: To
lock
file, a file named
file.lock is created.
OPTIONS¶
- -t
- Just try. 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, dotlock will
break that lock by removing the lockfile.
- -u
- Unlock. dotlock will remove file.lock.
- -d
- Delete. dotlock will lock file, remove it if
it has length 0, and afterwards remove file.lock.
- -r retries
- This command line option tells 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.
dotlock waits one second between successive locking attempts.
FILES¶
- file.lock
- The lock file dotlock generates.
SEE ALSO¶
fcntl(2),
flock(2),
lockfile(1),
lbdb-fetchaddr(1)
DIAGNOSTICS¶
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 dotlock is invoked with the -f
command line option, dotlock won't generate this error, but break
other processes' locks.
- 4 - DL_EX_NEED_RPIVS
- This return value only occurs if dotlock has been
invoked with the -t command line option. It means that
dotlock will have to use its group mail privileges to lock
file.
- 5 - DL_EX_IMPOSSIBLE
- This return value only occurs if dotlock has been
invoked with the -t command line option. It means that
dotlock is unable to lock file.
NOTES¶
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,
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¶
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@guug.de>