Mercurial > trustbridge

annotate common/linuxlockfile.c @ 1005:4b4fb980272b

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(manual) Updated all sections in help manual.
author Emanuel Schuetze <emanuel@intevation.de>
date Mon, 01 Sep 2014 15:39:52 +0200
parents 20ca94680003
children a974b61a5cce
rev   line source
782
20ca94680003 Implemented detection of running instance on linux using a lock file.
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1 #ifndef WIN32
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2
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3 #include <fcntl.h>
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4 #include <stdio.h>
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5 #include <sys/types.h>
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6 #include <unistd.h>
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7
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8 #include "logging.h"
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9
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10 int
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11 open_lockfile(char *path)
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12 {
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13 int fd;
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14 char pidstr[20];
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15 size_t pidstrlen;
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16 struct flock lk;
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17 fd = open(path, O_RDWR | O_CREAT, 0600);
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18 if (fd != -1)
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19 {
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20 /* Get an exclusive lock on the whole file. */
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21 lk.l_type = F_WRLCK;
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22 lk.l_whence = SEEK_SET;
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23 lk.l_start = 0;
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24 lk.l_len = 0;
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25 if (fcntl(fd, F_SETLK, &lk) != -1)
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26 {
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27 /* FIXME: For extra security we should check if there is
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28 already a pid in the file. If so we should check in
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29 /proc/$PID if there is still a process of the same name
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30 as ours running... */
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31 ftruncate(fd, 0);
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32 pidstrlen = (size_t)snprintf(pidstr, sizeof(pidstr), "%d", getpid());
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33 write(fd, pidstr, pidstrlen);
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34 }
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35 else
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36 {
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37 /* Lock can not be acquired. Bail out... */
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38 close(fd);
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39 DEBUGPRINTF("Could not get an exclusive lock on %s.\n", path);
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40 return -1;
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41 }
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42 }
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43 else
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44 {
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45 DEBUGPRINTF("Failed to open lock file: %s.\n", path);
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46 }
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47 return fd;
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48 }
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49
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50 void
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51 close_lockfile(int fd)
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52 {
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53 struct flock lk;
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54
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55 /* Delete the PID from file. */
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56 /* We do this instead of trying to unlink the file. */
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57 ftruncate(fd, 0);
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58
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59 /* Remove lock from the file. */
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60 lk.l_type = F_UNLCK;
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61 lk.l_whence = SEEK_SET;
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62 lk.l_start = 0;
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63 lk.l_len = 0;
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64 if (fcntl(fd, F_SETLK, &lk) == -1)
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65 {
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66 /* Lock can not be removed?!? WTF? */
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67 DEBUGPRINTF("Could not remove lock from pid file. STRANGE!\n");
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68 }
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69 close(fd);
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70 }
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71
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72 #endif /* Not WIN32 */
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