launcher.c

这个是学习嵌入式开发的重要例子

#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <sys/types.h>

void child_process_main(int argc, char **argv);

int main(int argc, char **argv)
{
  pid_t pid;

  if (argc < 2)
  {
    fprintf(stderr, "Please specify a command and it's parameters.\n");
    exit(1);
  }

#if 0
  if (setsid() == (pid_t) - 1)
  {
    fprintf(stderr, "setsid() failed: %s\n", strerror(errno));
    exit(1);
  }
#endif

  if ((pid = fork()) < 0)
  {
    fprintf(stderr, "fork() failed: %s\n", strerror(errno));
    exit(1);
  }
  else if (pid == 0)
  {
    //pid_t setsid(void);
    //setpgid();

#if 0
    close(0);
    close(1);
    close(2);
#endif

#if 1
    if (setsid() == (pid_t) - 1)
    {
      fprintf(stderr, "setsid() failed: %s\n", strerror(errno));
      exit(1);
    }
#endif

    child_process_main(argc, argv);
    exit(0);
  }

  pid_t returned_pid;
  int status;

  returned_pid = wait(&status);

  if (returned_pid < 0)
  {
    fprintf(stderr, "wait() failed: %s\n", strerror(errno));
    exit(1);
  }
  else
  {
    if (returned_pid == pid)
    {
      fprintf(stdout, "child process terminated.\n");
    }
  }

  for (;;)
  {
    char *msg = "************launcher is alive.*************\n";

    write(1, msg, strlen(msg));
    sleep(1);
  }

  return 0;
}

void child_process_main(int argc, char **argv)
{
  int return_code;
  char *v[1024];

  //return_code = execl("/bin/ls", "/bin/ls", "-l", (char *) 0);
  //char *v[] = { "ls", NULL };
  //return_code = execlp("ls1", "ls1", (char *) 0);

  int i;

  for (i = 1; i < argc; i++)
  {
    v[i - 1] = argv[i];
  }

  v[argc] = NULL;

  return_code = execvp(argv[1], v);

  if (return_code < 0)
  {
    fprintf(stderr, "excel() failed: %s\n", strerror(errno));
  }
  else
  {
    fprintf(stderr, "excel() successed.\n");
  }
}