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Rev Author # Line
1 perry 1 dotlock
2 !!!dotlock
3 NAME
4 SYNOPSIS
5 DESCRIPTION
6 OPTIONS
7 FILES
8 SEE ALSO
9 DIAGNOSTICS
10 NOTES
11 HISTORY
12 AUTHOR
13 ----
14 !!NAME
15
16
17 mutt_dotlock - Lock mail spool files.
18 !!SYNOPSIS
19
20
21 __mutt_dotlock__ [[-t|-f|-u|-d] [[-p] [[-r ''retries'']
22 ''file''
23 !!DESCRIPTION
24
25
26 __mutt_dotlock__ implements the traditional mail spool
27 file locking method: To lock ''file'', a file named
28 ''file''.lock is created. The program operates with group
29 mail privileges if necessary.
30 !!OPTIONS
31
32
33 -t
34
35
36 Just try. __mutt_dotlock__ won't actually lock a file,
37 but inform the invoking process if it's at all possible to
38 lock ''file''.
39
40
41 -f
42
43
44 Force the lock. If another process holds a lock on
45 ''file'' longer than a certain amount of time,
46 __mutt_dotlock__ will break that lock by removing the
47 lockfile.
48
49
50 -u
51
52
53 Unlock. __mutt_dotlock__ will remove
54 ''file''.lock.
55
56
57 -d
58
59
60 Delete. __mutt_dotlock__ will lock ''file'', remove it
61 if it has length 0, and afterwards remove
62 ''file''.lock.
63
64
65 -p
66
67
68 Use privileges. If given this option, __mutt_dotlock__
69 will operate with group mail privileges when creating and
70 deleting lock files.
71
72
73 -r ''retries''
74
75
76 This command line option tells __mutt_dotlock__ to try
77 locking ''retries'' times before giving up or (if invoked
78 with the __-f__ command line option) break a lock. The
79 default value is 5. __mutt_dotlock__ waits one second
80 between successive locking attempts.
81 !!FILES
82
83
84 ''file''.lock
85
86
87 The lock file __mutt_dotlock__ generates.
88 !!SEE ALSO
89
90
91 fcntl(2), flock(2), lockfile(1),
92 mutt(1)
93 !!DIAGNOSTICS
94
95
96 __mutt_dotlock__ gives all diagnostics in its return
97 values:
98
99
100 __0 - DL_EX_OK__
101
102
103 The program was successful.
104
105
106 __1 - DL_EX_ERROR__
107
108
109 An unspecified error such as bad command line parameters,
110 lack of system memory and the like has occured.
111
112
113 __3 - DL_EX_EXIST__
114
115
116 The user wants to lock a file which has been locked by
117 another process already. If __mutt_dotlock__ is invoked
118 with the __-f__ command line option, __mutt_dotlock__
119 won't generate this error, but break other processes'
120 locks.
121
122
123 __4 - DL_EX_NEED_RPIVS__
124
125
126 This return value only occurs if __mutt_dotlock__ has
127 been invoked with the __-t__ command line option. It
128 means that __mutt_dotlock__ will have to use its group
129 mail privileges to lock ''file''.
130
131
132 __5 - DL_EX_IMPOSSIBLE__
133
134
135 This return value only occurs if __mutt_dotlock__ has
136 been invoked with the __-t__ command line option. It
137 means that __mutt_dotlock__ is unable to lock ''file''
138 even with group mail privileges.
139 !!NOTES
140
141
142 __mutt_dotlock__ tries to implement an NFS-safe
143 dotlocking method which was borrowed from __lockfile__
144 (1).
145
146
147 If the user can't open ''file'' for reading with his
148 normal privileges, __mutt_dotlock__ will return the
149 __DL_EX_ERROR__ exit value to avoid certain attacks
150 against other users' spool files. The code carefully avoids
151 race conditions when checking permissions; for details of
152 all this see the comments in dotlock.c.
153 !!HISTORY
154
155
156 __mutt_dotlock__ is part of the Mutt mail user agent
157 package. It has been created to avoid running mutt with
158 group mail privileges.
159 !!AUTHOR
160
161
162 Thomas Roessler
163 ----
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