Jak naprogramovat jednoduchy demon

[Milan Kopacka]

On Thu, 2 Dec 1999, Petr Blaha wrote:

> Potreboval bych poradit jak naprogramovat demona. Udelal jsem si programek
> LCDpulse ktery rozvecuje diody pres paralerni port v zavislosti na
> okamzitem
> vytizeni CPU. Blika to pekne, ale potreboval bych poradit jak
> to udelat aby to byl demon a mohl se zpoustet pomoci scriptu rc.local
> 
> diky za rady Petr Blaha (engeneer na h-tech.cz)
> 
> Zde je hlavni cast programu LEDpulse, ktery bezi v nekonecne smycce:

Nekde pred nekonecnou smyckou, ale za vypisy na stdout/err pouzijte neco
jako

if (daemon(0,0)==-1){
  perror("daemon");
}

SYNOPSIS
     #include <stdlib.h>

     int
     daemon(int nochdir, int noclose)

DESCRIPTION
     The daemon() function is for programs wishing to detach themselves
     from the controlling terminal and run in the background as system
     daemons.

     Unless the argument nochdir is non-zero, daemon() changes the current
     working directory to the root (``/'').

     Unless the argument noclose is non-zero, daemon() will redirect
     standard input, standard output and standard error to ``/dev/null''.

ERRORS
     If an error occurs, daemon() returns -1 and sets the global variable
     errno to any of the errors specified for the library functions
     fork(2) and setsid(2).



  Milan Kopacka