annotate src/daemon.c @ 77:c6ba792f1a9a

systemd only
author Carl Byington <carl@five-ten-sg.com>
date Wed, 15 Jul 2020 13:58:42 -0700
parents 9e9f09cf411c
children
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1 /*Add by Sergey Shapovalov */
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2 #include <unistd.h>
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3 #include <stdlib.h>
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4 #include <fcntl.h>
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5 #include <signal.h>
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6 #include <sys/types.h>
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7 #include <sys/wait.h>
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8 #include <errno.h>
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9
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10 /* closeall() -- close all FDs >= a specified value */
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11
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12 void closeall(int fd)
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13 {
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14 int fdlimit = sysconf(_SC_OPEN_MAX);
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15
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16 while (fd < fdlimit)
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17 close(fd++);
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18 }
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19
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20 /* daemon() - detach process from user and disappear into the background
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21 * returns -1 on failure, but you can't do much except exit in that case
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22 * since we may already have forked. This is based on the BSD version,
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23 * so the caller is responsible for things like the umask, etc.
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24 */
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25
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26 /* believed to work on all Posix systems */
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27
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28 int daemon(int nochdir, int noclose)
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29 {
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30 switch (fork())
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31 {
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32 case 0: break;
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33 case -1: return -1;
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34 default: _exit(0); /* exit the original process */
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35 }
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36
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37 if (setsid() < 0) /* shoudn't fail */
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38 return -1;
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39
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40 /* dyke out this switch if you want to acquire a control tty in */
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41 /* the future -- not normally advisable for daemons */
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42
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43 switch (fork())
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44 {
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45 case 0: break;
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46 case -1: return -1;
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47 default: _exit(0);
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48 }
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49
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50 if (!nochdir)
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51 chdir("/");
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52
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53 if (!noclose)
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54 {
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55 closeall(0);
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56 open("/dev/null",O_RDWR);
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57 dup(0); dup(0);
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58 }
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59
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60 return 0;
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61 }