Greetings;
I am trying to create a background application (starts with system
startup, and keeps running in the background ) . the only solution i
found is to make it as daemon.
searching the internet about how to create a daemon
<http://www.enderunix.org/docs/eng/daemon.php> , I built a small app
around my findings.
Qt Code:
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#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <signal.h>
#include <unistd.h>
#include "globaldefs.h"
void log_message(char *filename,char *message)
{
FILE *logfile;
logfile=fopen(filename,"a");
if(!logfile) return;
fprintf(logfile,"%s\n",message);
fclose(logfile);
}
/**
a signal handler for the Linux signals sent to daemon process,
for more signals, refer to
http://www.comptechdoc.org/os/linux/programming/linux_pgsignals.html
*/
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");
break;
}
}
/**
create background process out of the application, source code taken from:
http://www.enderunix.org/docs/eng/daemon.php
with some minor modifications
*/
void init_daemon()
{
int i,lfp;
char str[10];
if(getppid()==1)
return; /* already a daemon */
i=fork();
if (i<0)
exit(1); /* fork error */
if (i>0)
exit(0); /* parent exits */
/* child (daemon) continues */
setsid(); /* obtain a new process group */
for (i=getdtablesize();i>=0;--i)
close(i); /* close all descriptors */
i=open("/dev/null",O_RDWR); dup(i); dup(i); /* handle standart I/O */
umask(027); /* set newly created file permissions */
chdir(RUNNING_DIR); /* change running directory */
lfp=open(LOCK_FILE,O_RDWR|O_CREAT,0640);
if (lfp<0)
exit(1); /* can not open */
if (lockf(lfp,F_TLOCK,0)<0)
exit(0); /* can not lock */
/* first instance continues */
sprintf(str,"%d\n",getpid());
write(lfp,str,strlen(str)); /* record pid to lockfile */
signal(SIGCHLD,SIG_IGN); /* ignore child */
signal(SIGTSTP,SIG_IGN); /* ignore tty signals */
signal(SIGTTOU,SIG_IGN);
signal(SIGTTIN,SIG_IGN);
signal(SIGHUP,signal_handler); /* catch hangup signal */
signal(SIGTERM,signal_handler); /* catch kill signal */
}
int main(int argc, char *argv[])
{
// first, create the daemon
init_daemon();
QCoreApplication <http://doc.trolltech.com/latest/QCoreApplication.html>
a(argc, argv);
return a.exec();
}
the code doesn't handle signals (for example, a termination signal). So,
when I run it from the command line, and try to kill it, it refuses to
get killed!!! the only way to kill the process is to restart the phone !!
I really suspect that creating a QCoreApplication instance in the main
method forks a new process other than the one i forked in the
init_daemom() method. But i can't find any clue . On the other hand, i
can't init my qt app without creating a QCoreApplication instance -says
qt documentation.
When I try to debug the application. it fails to fork a new process thus
exit() is issued and the debugging session terminates.
I am using Qt 4.5 and the phone's libqt version is 4.5.3
What am I missing? can there be anything done to make my Qt application
run as a daemon process ?? Am i using a wrong way to do so?
thanks in advance;
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