Creation of Daemons under Linux

Recently Learning Linux C programming

I saw the creation of the daemon, it was fun,

Test environment Ubuntu 15.04

The test code is posted below

#include <stdio.h>#include<stdlib.h>#include<unistd.h>#include<signal.h>#include<sys/param.h>#include<sys/stat.h>#include<time.h>#include<syslog.h>intInit_pro (void ){    intpid//Process Number    inti; /*Ignore terminal IO signal, stop signal*/signal (Sigttou, sig_ign);    Signal (Sigttin, sig_ign);    Signal (SIGTSTP, sig_ign);    Signal (SIGHUP, sig_ign); /*open a new process under the current process*/PID=Fork (); //if pid>0 returns the process ID of the parent process, ends the parent process    if(PID >0) {exit (0);//ends the parent process, making the child process a background process    }    Else    //if the PID is less than 0, the child process fails to turn back    if(PID <0 )    {        return-1; }    //Create a new process group in which the child process becomes the first process in the process, leaving the process out of all endpointsSetsid (); //once again, create a new sub-process by fork, which is to create a new subprocess under the sub-process you just created.//The goal is to ensure that the process is not the process leader and that the process cannot open a terminalPID =Fork (); if(PID >0) {exit (0);//if the PID of the parent process (that is, the previous subprocess) is returned then end the process    }    Else    if(PID <0 )    {        return-1; }    //What is Nofile    //Close all file descriptors that are not required to inherit from the parent process//What isFile Descriptor     for(i =0; i < Nofile; Close (i++) ); //change the working directory so that the process does not contact any file system//There's actually only one last open subprocess left.ChDir"/"); //Set the file screen Word to 0Umask0); //Ignoring SIGCHLD signalssignal (SIGCHLD, sig_ign); return 0;}intMainintargcChar**argv)    {time_t now;    Init_pro (); Syslog (Log_user| Log_info,"Test Daemon! \ n");  while(1)    {        /*Code*/Sleep (8); Time (&Now ); Syslog (Log_user| Log_info,"system time: \t%s\t\t\n", CTime (&Now )); }}

Note that before using syslog, you first need to configure the/etc/rsyslog.conf file to add User*/var/log/test.log at the end of the file

Then restart the Rsyslog service

Compile run

When we open the Test.log, we'll find that every 8 seconds, he ticks back.

The use of Ps-ef can be observed

Creation of Daemons under Linux