3 Copyright (C) 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
5 Authors: 2003 Adam Byrtek
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2 of the License, or
10 (at your option) any later version.
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software
19 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
25 * \brief Source: file locking
29 * Locking scheme is based on a documentation found
30 * in JED editor sources. Abstract from lock.c file (by John E. Davis):
32 * The basic idea here is quite simple. Whenever a buffer is attached to
33 * a file, and that buffer is modified, then attempt to lock the
34 * file. Moreover, before writing to a file for any reason, lock the
35 * file. The lock is really a protocol respected and not a real lock.
36 * The protocol is this: If in the directory of the file is a
37 * symbolic link with name ".#FILE", the FILE is considered to be locked
38 * by the process specified by the link.
43 #include <signal.h> /* kill() */
46 #include <sys/types.h>
55 #include "lib/global.h"
56 #include "lib/vfs/mc-vfs/vfs.h"
57 #include "lib/util.h" /* tilde_expand() */
60 #include "src/wtools.h" /* query_dialog() */
63 #define PID_BUF_SIZE 10
70 /** \fn static char * lock_build_name (void)
71 * \brief builds user@host.domain.pid string (need to be freed)
72 * \return a pointer to lock filename
75 lock_build_name (void)
78 const char *user
= NULL
;
81 pw
= getpwuid (getuid ());
82 if (pw
) user
= pw
->pw_name
;
83 if (!user
) user
= getenv ("USER");
84 if (!user
) user
= getenv ("USERNAME");
85 if (!user
) user
= getenv ("LOGNAME");
88 /** \todo Use FQDN, no clean interface, so requires lot of code */
89 if (gethostname (host
, BUF_SIZE
- 1) == -1)
92 return g_strdup_printf ("%s@%s.%d", user
, host
, (int) getpid ());
96 lock_build_symlink_name (const char *fname
)
98 char *fname_copy
, *symlink_name
;
99 char absolute_fname
[PATH_MAX
];
101 if (mc_realpath (fname
, absolute_fname
) == NULL
)
104 fname
= x_basename (absolute_fname
);
105 fname_copy
= g_strdup (fname
);
106 absolute_fname
[fname
- absolute_fname
] = '\0';
107 symlink_name
= g_strconcat (absolute_fname
, ".#", fname_copy
, (char *) NULL
);
113 /* Extract pid from user@host.domain.pid string */
114 static struct lock_s
*
115 lock_extract_info (const char *str
)
119 static char pid
[PID_BUF_SIZE
], who
[BUF_SIZE
];
120 static struct lock_s lock
;
124 for (p
= str
+ len
- 1; p
>= str
; p
--)
128 /* Everything before last '.' is user@host */
130 for (s
= str
; s
< p
&& i
< BUF_SIZE
; s
++)
134 /* Treat text between '.' and ':' or '\0' as pid */
136 for (p
= p
+ 1; (p
< str
+ len
) && (*p
!= ':') && (i
< PID_BUF_SIZE
); p
++)
140 lock
.pid
= (pid_t
) atol (pid
);
145 /* Extract user@host.domain.pid from lock file (static string) */
147 lock_get_info (const char *lockfname
)
150 static char buf
[BUF_SIZE
];
152 cnt
= readlink (lockfname
, buf
, BUF_SIZE
- 1);
153 if (cnt
== -1 || *buf
== '\0')
160 /* Tries to raise file lock
161 Returns 1 on success, 0 on failure, -1 if abort
162 Warning: Might do screen refresh and lose edit->force */
164 lock_file (const char *fname
)
166 char *lockfname
, *newlock
, *msg
, *lock
;
168 struct lock_s
*lockinfo
;
171 /* Just to be sure (and don't lock new file) */
172 if (fname
== NULL
|| *fname
== '\0')
175 fname
= tilde_expand (fname
);
177 /* Locking on VFS is not supported */
178 if (!vfs_file_is_local (fname
))
184 /* Check if already locked */
185 lockfname
= lock_build_symlink_name (fname
);
187 if (lockfname
== NULL
)
190 if (lstat (lockfname
, &statbuf
) == 0) {
191 lock
= lock_get_info (lockfname
);
196 lockinfo
= lock_extract_info (lock
);
198 /* Check if locking process alive, ask user if required */
199 if (lockinfo
->pid
== 0
200 || !(kill (lockinfo
->pid
, 0) == -1 && errno
== ESRCH
)) {
203 ("File \"%s\" is already being edited.\n"
204 "User: %s\nProcess ID: %d"), x_basename (lockfname
) + 2,
205 lockinfo
->who
, (int) lockinfo
->pid
);
206 /* TODO: Implement "Abort" - needs to rewind undo stack */
208 (_("File locked"), msg
, D_NORMAL
, 2, _("&Grab lock"),
209 _("&Ignore lock"))) {
223 /* Create lock symlink */
224 newlock
= lock_build_name ();
225 symlink_ok
= (symlink (newlock
, lockfname
) != -1);
229 return symlink_ok
? 1 : 0;
232 /* Lowers file lock if possible
235 unlock_file (const char *fname
)
237 char *lockfname
, *lock
;
240 /* Just to be sure */
241 if (fname
== NULL
|| *fname
== '\0')
244 fname
= tilde_expand (fname
);
245 lockfname
= lock_build_symlink_name (fname
);
248 if (lockfname
== NULL
)
251 /* Check if lock exists */
252 if (lstat (lockfname
, &statbuf
) == -1) {
257 lock
= lock_get_info (lockfname
);
259 /* Don't touch if lock is not ours */
260 if (lock_extract_info (lock
)->pid
!= getpid ()) {