#include <signal.h>
#include <unistd.h>
#include <errno.h>
#include <signal.h>
#include <fcntl.h>
#include <stdio.h>
#include <sys/times.h>
#include <sys/wait.h>

void exec_truc();
void exec_wait();

int main() {
  exec_truc();
  exec_wait();
}

int    chld_ofd = 0;
FILE*  chld_ostream = 0;
int    chld_pid = 0;

#define EXECCMD_PIPE_READ 0
#define EXECCMD_PIPE_WRITE 1

void exec_truc() {
  int out[ 2 ];
  
  /* Create pipes for collecting child output. */
  if ( pipe( out ) < 0 ) exit( -1 );
  /* Child does not need the read pipe ends used by the parent. */
  fcntl( out[ EXECCMD_PIPE_READ ], F_SETFD, FD_CLOEXEC );
  
  if ( ( chld_pid = vfork() ) == -1 )  exit( -1 );
  
  if ( chld_pid == 0 ) {  // TASK
    int const pid = getpid();
    
    /* Redirect stdout and stderr to pipes inherited from the parent. */
    dup2( out[ EXECCMD_PIPE_WRITE ], STDOUT_FILENO );
    close( out[ EXECCMD_PIPE_WRITE ] );
    
    setpgid( pid, pid );
    
    char const * argv[ 42 ];
    argv[0] = "/bin/sh";
    argv[1] = "-c";
    argv[2] = "    LD_LIBRARY_PATH=/gpfs/scratch/alainm/view/boost/bin.v2/libs/mpi/build/intel-linux/debug:/gpfs/scratch/alainm/view/boost/bin.v2/libs/serialization/build/intel-linux/debug:/softs/intel/composer_xe_2015.0.090/bin/lib:/softs/intel/composer_xe_2015.0.090/lib/intel64:$LD_LIBRARY_PATH\n"
      " export LD_LIBRARY_PATH\n"
      " mpiexec.hydra -n 1 echo argh\n";
      " status=$?\n"
      " exit $status\n"
      ;
    argv[3] = 0;
    execvp( argv[0], (char * *)argv );
    exit( 127 );
  } else {
    setpgid( chld_pid, chld_pid );
    /* Parent not need the write pipe ends used by the child. */
    close( out[ EXECCMD_PIPE_WRITE ] );
    /* Set both pipe read file descriptors to non-blocking. */
    fcntl( out[ EXECCMD_PIPE_READ ], F_SETFL, O_NONBLOCK );
    /* Parent reads from out[ EXECCMD_PIPE_READ ]. */
    chld_ofd = out[ EXECCMD_PIPE_READ ];
    if ((chld_ostream = fdopen( chld_ofd, "rb" )) == 0) exit(-1);
  }
}

void exec_wait() {
  while(1) {
    /* Prepare file descriptor information for use in select(). */
    fd_set fds;
    FD_ZERO( &fds );
    FD_SET( chld_ofd, &fds );
    /* select() will wait for I/O on a descriptor, a signal, or timeout. */
    {
      /* disable child termination signals while in select */
      int ret;
      sigset_t sigmask;
      sigemptyset(&sigmask);
      sigaddset(&sigmask, SIGCHLD);
      sigprocmask(SIG_BLOCK, &sigmask, NULL);
      while ( ( ret = select( chld_ofd + 1, &fds, 0, 0, 0 ) ) == -1 )
        if ( errno != EINTR )
          break;
      /* restore original signal mask by unblocking sigchld */
      sigprocmask(SIG_UNBLOCK, &sigmask, NULL);
      if ( ret <= 0 )
        continue;
    }
  }
}