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June 19, 2011 07:24
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A sample Daemon program in C
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#include <stdio.h> | |
#include <fcntl.h> | |
#include <signal.h> | |
#include <unistd.h> | |
#include <stdlib.h> | |
#include <string.h> | |
#define RUNNING_DIR "/tmp" | |
#define LOCK_FILE "daemond.lock" | |
#define LOG_FILE "daemond.log" | |
/* | |
* daemon.c | |
* | |
* Copyright 2010 Vasudev Kamath <kamathvasudev@gmail.com> | |
* | |
* This program is free software; you can redistribute it and/or modify | |
* it under the terms of the GNU Lesser General Public License as published by | |
* the Free Software Foundation; either version 3 of the License, or | |
* (at your option) any later version. | |
* | |
* This program is distributed in the hope that it will be useful, | |
* but WITHOUT ANY WARRANTY; without even the implied warranty of | |
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
* GNU General Public License for more details. | |
* | |
* You should have received a copy of the GNU General Public License | |
* along with this program; if not, write to the Free Software | |
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, | |
* MA 02110-1301, USA. | |
*/ | |
void log_message(char *filename,char *message){ | |
FILE *logfile; | |
logfile = fopen(filename,"a"); | |
if(!logfile) | |
return; | |
fprintf(logfile,"%s",message); | |
fclose(logfile); | |
} | |
void signal_handler(int sig){ | |
switch(sig){ | |
case SIGHUP: | |
log_message(LOG_FILE,"Hangup Signal Catched"); | |
break; | |
case SIGTERM: | |
log_message(LOG_FILE,"Terminate Signal Catched"); | |
exit(0); | |
break; | |
} | |
} | |
void daemonize(){ | |
int i,lfp; | |
char str[10]; | |
if(getppid() == 1) | |
return; | |
i = fork(); | |
if(i < 0) | |
exit(1); | |
if(i > 0) | |
exit(0); | |
setsid(); | |
for(i = getdtablesize(); i >= 0; --i) | |
close(i); | |
i = open("/dev/null",O_RDWR); | |
dup(i); | |
dup(i); | |
umask(027); | |
chdir(RUNNING_DIR); | |
lfp = open(LOCK_FILE,O_RDWR|O_CREAT,0640); | |
if(lfp < 0) | |
exit(1); | |
if(lockf(lfp,F_TLOCK,0) < 0) | |
exit(1); | |
sprintf(str,"%d\n",getpid()); | |
write(lfp,str,strlen(str)); | |
signal(SIGCHLD,SIG_IGN); | |
signal(SIGTSTP,SIG_IGN); | |
signal(SIGTTOU,SIG_IGN); | |
signal(SIGTTIN,SIG_IGN); | |
signal(SIGHUP,signal_handler); | |
signal(SIGTERM,signal_handler); | |
} | |
int main(int argc,char **argv){ | |
daemonize(); | |
while(1) | |
sleep(1); | |
} |
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What does it mean getppid()==1