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106 lines
3.7 KiB
C
106 lines
3.7 KiB
C
/*
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* This file is part of the Snippets project.
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* Copyright 2024 Edward V. Emelianov <edward.emelianoff@gmail.com>.
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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// example of simplest daemon: search for running process, daemonize if all OK and herd its child
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#include <linux/prctl.h>
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#include <sys/prctl.h>
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#include <sys/wait.h>
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#include <usefull_macros.h>
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static pid_t childpid = 0;
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typedef struct{
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int help;
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int verbose;
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int nodaemon;
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char *logfile;
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char *pidfile;
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} parameters;
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static parameters G = {0};
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static sl_option_t cmdlnopts[] = {
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{"help", NO_ARGS, NULL, 'h', arg_int, APTR(&G.help), "show this help"},
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{"verbose", NO_ARGS, NULL, 'v', arg_none, APTR(&G.verbose), "verbose level (each -v adds 1)"},
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{"logfile", NEED_ARG, NULL, 'l', arg_string, APTR(&G.logfile), "log file name (FULL path!!!)"},
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{"pidfile", NEED_ARG, NULL, 'p', arg_string, APTR(&G.pidfile), "PID-file name (FULL path!!!)"},
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{"nodaemon", NO_ARGS, NULL, 0, arg_int, APTR(&G.nodaemon), "don't daemonize"},
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end_option
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};
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void sl_iffound_deflt(pid_t pid){
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WARNX("Another copy of this process found, pid=%d. Exit.", pid);
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exit(1); // don't run `signals` to protect foreign PID-file from removal
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}
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void signals(int signo){
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if(childpid){ // this is a main process!
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LOGERR("Main process exits with status %d", signo);
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// main process have nothing to cleanup, just remove PID-file
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if(G.pidfile) unlink(G.pidfile);
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}else{ // this is child
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LOGERR("Killed with status %d, clearing", signo);
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// here we can close everything and make cleanup
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}
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usleep(1000);
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LOGERR("Exited");
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exit(signo);
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}
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int main(int argc, char **argv){
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sl_init();
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sl_parseargs(&argc, &argv, cmdlnopts);
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if(G.help) sl_showhelp(-1, cmdlnopts);
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sl_loglevel_e lvl = G.verbose + LOGLEVEL_ERR;
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if(lvl >= LOGLEVEL_AMOUNT) lvl = LOGLEVEL_AMOUNT - 1;
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sl_check4running(NULL, G.pidfile);
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LOGMSG("Hello, I'm started");
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if(G.logfile) OPENLOG(G.logfile, lvl, 1);
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if(!G.nodaemon){
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green("Daemonize..\n");
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LOGMSG("Daemonize");
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// and ignore SIGHUP
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if(sl_daemonize()){
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WARN("sl_daemonize() failed");
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LOGERR("Can't daemonize");
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}
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}
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signal(SIGTERM, signals); // kill (-15) - quit
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signal(SIGINT, signals); // ctrl+C - quit
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signal(SIGQUIT, signals); // ctrl+\ - quit
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signal(SIGTSTP, SIG_IGN); // ignore ctrl+Z
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while(1){ // guard for dead processes
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childpid = fork();
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if(childpid){
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LOGMSG("create child with PID %d\n", childpid);
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DBG("Created child with PID %d\n", childpid);
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wait(NULL);
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WARNX("Child %d died\n", childpid);
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LOGWARN("Child %d died\n", childpid);
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sleep(1);
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}else{
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prctl(PR_SET_PDEATHSIG, SIGTERM); // send SIGTERM to child when parent dies
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break; // go out to normal functional
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}
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}
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LOGMSG("Here is the child process; sleep for 1 second and die");
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sleep(1);
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return 0;
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}
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