#include <signal.h>
#include <iostream>

using std::cout;
using std::endl;
using std::flush;

static const int MSG_BUF = 160;
static char msgbuf[ MSG_BUF ];
static char *puthead( void ) {
   struct timespec t;
   clock_gettime( CLOCK_REALTIME, &t );
   int sec = t.tv_sec % 60, min = t.tv_sec % 3600 / 60,
       ms = t.tv_nsec / 1000000, mks = t.tv_nsec % 1000000 / 1000;
   sprintf( msgbuf, "[%02d:%02d.%03d.%03d] %d: ", min, sec, ms, mks, getpid() );
   return msgbuf + strlen( msgbuf );
};

static void chend( int ) {
   sprintf( puthead(), "oh, my God - my child is dead!\n" );
   cout << msgbuf << flush;
};

int main( int argc, char* argv[] ) {
   int c, msec = 300, level = 0;
   while( ( c = getopt( argc, argv, "c:t:" ) ) != -1 ) {
      switch( c ) {
         case 'c': level = atoi( optarg ); break;
         case 't': msec = atoi( optarg ); break;
         default : exit( EXIT_FAILURE );
      };
   };
   signal( SIGCHLD, chend );
   pid_t id; // = -1;
   int w = 4, j = -1;
   while( --level > 0 && ( id = fork() ) == 0 ) { w += j; j = ( j < 0 ? 2 : -1 );  };
   sprintf( puthead(), "start - my parent is %d\n", getppid() );
   cout << msgbuf << flush;
   for( int i = 0; i < w; i++ )
      if( delay( msec ) != 0 ) --i;
      else {
         sprintf( puthead(), "continue %d - parent is %d\n", i + 1 , getppid() );
         cout << msgbuf << flush;
      };
   sprintf( puthead(), "finished\n" );
   cout << msgbuf << flush;
   exit( EXIT_SUCCESS );
};

# ./zomby2 -c4 -t2000
[38:04.744.723] 6467647: start - my parent is 4710443
[38:04.746.723] 6471744: start - my parent is 6467647
[38:04.748.722] 6471745: start - my parent is 6471744
[38:04.748.722] 6471746: start - my parent is 6471745
[38:06.746.417] 6467647: continue 1 - parent is 4710443
[38:06.748.416] 6471744: continue 1 - parent is 6467647
[38:06.750.416] 6471745: continue 1 - parent is 6471744
[38:06.750.416] 6471746: continue 1 - parent is 6471745
[38:08.748.110] 6467647: continue 2 - parent is 4710443
[38:08.750.110] 6471744: continue 2 - parent is 6467647
[38:08.752.110] 6471745: continue 2 - parent is 6471744
[38:08.752.110] 6471746: continue 2 - parent is 6471745
[38:10.749.804] 6467647: continue 3 - parent is 4710443
[38:10.751.804] 6471744: continue 3 - parent is 6467647
[38:10.751.804] 6471744: finished
[38:10.752.804] 6467647: oh, my God - my child is dead!
[38:10.753.804] 6471745: continue 3 - parent is 6471744
[38:10.753.804] 6471746: continue 3 - parent is 6471745
[38:12.754.497] 6467647: continue 4 - parent is 4710443
[38:12.754.497] 6467647: finished
[38:12.755.497] 6471745: continue 4 - parent is 6471744
[38:12.755.497] 6471746: continue 4 - parent is 6471745
[38:12.755.497] 6471746: finished
[38:12.756.497] 6471745: oh, my God - my child is dead!
# [38:14.758.191] 6471745: continue 5 - parent is 1
[38:14.758.191] 6471745: finished

#

# pidin
6467647   1 ./zomby2            10o NANOSLEEP
6471744     (Zombie)
6471745   1 ./zomby2            10o NANOSLEEP
6471746   1 ./zomby2            10o NANOSLEEP

#! /usr/bin/perl -w

use strict;
use POSIX;

my $proc;
my @program = ("wget","-c","-t","1","-T","10",
"http://download.xilinx.com/direct/webpack/91/WebPACK_SFD_91i.zip");

unless($proc = fork()){
  exec(@program);
}

for(;;){
  if(waitpid($proc,WNOHANG)){
    if($? != 0){
      unless($proc = fork()){
        exec(@program);
      }
    }
  }
  select(undef,undef,undef,0.1);
}