system.c

gnu tar 源码包。 tar 软件是 Unix 系统下的一个打包软件

    if (errno != EINTR)
      {
	waitpid_error (use_compress_program_option);
	break;
      }

  if (WIFSIGNALED (wait_status))
    {
      kill (child_pid, WTERMSIG (wait_status));
      exit_status = TAREXIT_FAILURE;
    }
  else if (WEXITSTATUS (wait_status) != 0)
    exit_status = WEXITSTATUS (wait_status);

  exit (exit_status);
}

/* Set ARCHIVE for uncompressing, then reading an archive.  */
pid_t
sys_child_open_for_uncompress (void)
{
  int parent_pipe[2];
  int child_pipe[2];
  pid_t grandchild_pid;
  pid_t child_pid;
  int wait_status;

  xpipe (parent_pipe);
  child_pid = xfork ();

  if (child_pid > 0)
    {
      /* The parent tar is still here!  Just clean up.  */

      archive = parent_pipe[PREAD];
      xclose (parent_pipe[PWRITE]);
      return child_pid;
    }

  /* The newborn child tar is here!  */

  program_name = _("tar (child)");

  xdup2 (parent_pipe[PWRITE], STDOUT_FILENO);
  xclose (parent_pipe[PREAD]);

  /* Check if we need a grandchild tar.  This happens only if either:
     a) we're reading stdin: to force unblocking;
     b) the file is to be accessed by rmt: compressor doesn't know how;
     c) the file is not a plain file.  */

  if (strcmp (archive_name_array[0], "-") != 0
      && !_remdev (archive_name_array[0])
      && is_regular_file (archive_name_array[0]))
    {
      /* We don't need a grandchild tar.  Open the archive and lauch the
	 uncompressor.  */

      archive = open (archive_name_array[0], O_RDONLY | O_BINARY, MODE_RW);
      if (archive < 0)
	open_fatal (archive_name_array[0]);
      xdup2 (archive, STDIN_FILENO);
      execlp (use_compress_program_option, use_compress_program_option,
	      "-d", (char *) 0);
      exec_fatal (use_compress_program_option);
    }

  /* We do need a grandchild tar.  */

  xpipe (child_pipe);
  grandchild_pid = xfork ();

  if (grandchild_pid == 0)
    {
      /* The newborn grandchild tar is here!  Launch the uncompressor.  */

      program_name = _("tar (grandchild)");

      xdup2 (child_pipe[PREAD], STDIN_FILENO);
      xclose (child_pipe[PWRITE]);
      execlp (use_compress_program_option, use_compress_program_option,
	      "-d", (char *) 0);
      exec_fatal (use_compress_program_option);
    }

  /* The child tar is still here!  */

  /* Prepare for unblocking the data from the archive into the
     uncompressor.  */

  xdup2 (child_pipe[PWRITE], STDOUT_FILENO);
  xclose (child_pipe[PREAD]);

  if (strcmp (archive_name_array[0], "-") == 0)
    archive = STDIN_FILENO;
  else
    archive = rmtopen (archive_name_array[0], O_RDONLY | O_BINARY,
		       MODE_RW, rsh_command_option);
  if (archive < 0)
    open_fatal (archive_name_array[0]);

  /* Let's read the archive and pipe it into stdout.  */

  while (1)
    {
      char *cursor;
      size_t maximum;
      size_t count;
      size_t status;

      clear_read_error_count ();

    error_loop:
      status = rmtread (archive, record_start->buffer, record_size);
      if (status == SAFE_READ_ERROR)
	{
	  archive_read_error ();
	  goto error_loop;
	}
      if (status == 0)
	break;
      cursor = record_start->buffer;
      maximum = status;
      while (maximum)
	{
	  count = maximum < BLOCKSIZE ? maximum : BLOCKSIZE;
	  if (full_write (STDOUT_FILENO, cursor, count) != count)
	    write_error (use_compress_program_option);
	  cursor += count;
	  maximum -= count;
	}
    }

  xclose (STDOUT_FILENO);

  /* Propagate any failure of the grandchild back to the parent.  */

  while (waitpid (grandchild_pid, &wait_status, 0) == -1)
    if (errno != EINTR)
      {
	waitpid_error (use_compress_program_option);
	break;
      }

  if (WIFSIGNALED (wait_status))
    {
      kill (child_pid, WTERMSIG (wait_status));
      exit_status = TAREXIT_FAILURE;
    }
  else if (WEXITSTATUS (wait_status) != 0)
    exit_status = WEXITSTATUS (wait_status);

  exit (exit_status);
}



static void
dec_to_env (char *envar, uintmax_t num)
{
  char buf[UINTMAX_STRSIZE_BOUND];
  char *numstr;

  numstr = STRINGIFY_BIGINT (num, buf);
  if (setenv (envar, numstr, 1) != 0)
    xalloc_die ();
}

static void
time_to_env (char *envar, struct timespec t)
{
  char buf[TIMESPEC_STRSIZE_BOUND];
  if (setenv (envar, code_timespec (t, buf), 1) != 0)
    xalloc_die ();
}

static void
oct_to_env (char *envar, unsigned long num)
{
  char buf[1+1+(sizeof(unsigned long)*CHAR_BIT+2)/3];

  snprintf (buf, sizeof buf, "0%lo", num);
  if (setenv (envar, buf, 1) != 0)
    xalloc_die ();
}

static void
str_to_env (char *envar, char const *str)
{
  if (str)
    {
      if (setenv (envar, str, 1) != 0)
	xalloc_die ();
    }
  else
    unsetenv (envar);
}

static void
chr_to_env (char *envar, char c)
{
  char buf[2];
  buf[0] = c;
  buf[1] = 0;
  if (setenv (envar, buf, 1) != 0)
    xalloc_die ();
}

static void
stat_to_env (char *name, char type, struct tar_stat_info *st)
{
  str_to_env ("TAR_VERSION", PACKAGE_VERSION);
  chr_to_env ("TAR_FILETYPE", type);
  oct_to_env ("TAR_MODE", st->stat.st_mode);
  str_to_env ("TAR_FILENAME", name);
  str_to_env ("TAR_REALNAME", st->file_name);
  str_to_env ("TAR_UNAME", st->uname);
  str_to_env ("TAR_GNAME", st->gname);
  time_to_env ("TAR_ATIME", st->atime);
  time_to_env ("TAR_MTIME", st->mtime);
  time_to_env ("TAR_CTIME", st->ctime);
  dec_to_env ("TAR_SIZE", st->stat.st_size);
  dec_to_env ("TAR_UID", st->stat.st_uid);
  dec_to_env ("TAR_GID", st->stat.st_gid);

  switch (type)
    {
    case 'b':
    case 'c':
      dec_to_env ("TAR_MINOR", minor (st->stat.st_rdev));
      dec_to_env ("TAR_MAJOR", major (st->stat.st_rdev));
      unsetenv ("TAR_LINKNAME");
      break;

    case 'l':
    case 'h':
      unsetenv ("TAR_MINOR");
      unsetenv ("TAR_MAJOR");
      str_to_env ("TAR_LINKNAME", st->link_name);
      break;

    default:
      unsetenv ("TAR_MINOR");
      unsetenv ("TAR_MAJOR");
      unsetenv ("TAR_LINKNAME");
      break;
    }
}

static pid_t global_pid;
static RETSIGTYPE (*pipe_handler) (int sig);

int
sys_exec_command (char *file_name, int typechar, struct tar_stat_info *st)
{
  int p[2];
  char *argv[4];

  xpipe (p);
  pipe_handler = signal (SIGPIPE, SIG_IGN);
  global_pid = xfork ();

  if (global_pid != 0)
    {
      xclose (p[PREAD]);
      return p[PWRITE];
    }

  /* Child */
  xdup2 (p[PREAD], STDIN_FILENO);
  xclose (p[PWRITE]);

  stat_to_env (file_name, typechar, st);

  argv[0] = "/bin/sh";
  argv[1] = "-c";
  argv[2] = to_command_option;
  argv[3] = NULL;

  execv ("/bin/sh", argv);

  exec_fatal (file_name);
}

void
sys_wait_command (void)
{
  int status;

  if (global_pid < 0)
    return;

  signal (SIGPIPE, pipe_handler);
  while (waitpid (global_pid, &status, 0) == -1)
    if (errno != EINTR)
      {
        global_pid = -1;
        waitpid_error (to_command_option);
        return;
      }

  if (WIFEXITED (status))
    {
      if (!ignore_command_error_option && WEXITSTATUS (status))
	ERROR ((0, 0, _("%lu: Child returned status %d"),
		(unsigned long) global_pid, WEXITSTATUS (status)));
    }
  else if (WIFSIGNALED (status))
    {
      WARN ((0, 0, _("%lu: Child terminated on signal %d"),
	     (unsigned long) global_pid, WTERMSIG (status)));
    }
  else
    ERROR ((0, 0, _("%lu: Child terminated on unknown reason"),
	    (unsigned long) global_pid));

  global_pid = -1;
}

int
sys_exec_info_script (const char **archive_name, int volume_number)
{
  pid_t pid;
  char *argv[4];
  char uintbuf[UINTMAX_STRSIZE_BOUND];
  int p[2];
  static RETSIGTYPE (*saved_handler) (int sig);
  
  xpipe (p);
  saved_handler = signal (SIGPIPE, SIG_IGN);

  pid = xfork ();

  if (pid != 0)
    {
      /* Master */

      int rc;
      int status;
      char *buf = NULL;
      size_t size = 0;
      FILE *fp;

      xclose (p[PWRITE]);
      fp = fdopen (p[PREAD], "r");
      rc = getline (&buf, &size, fp);
      fclose (fp);

      if (rc > 0 && buf[rc-1] == '\n')
	buf[--rc] = 0;

      while (waitpid (pid, &status, 0) == -1)
	if (errno != EINTR)
	  {
	    signal (SIGPIPE, saved_handler);
	    waitpid_error (info_script_option);
	    return -1;
	  }

      signal (SIGPIPE, saved_handler);
      
      if (WIFEXITED (status))
	{
	  if (WEXITSTATUS (status) == 0 && rc > 0)
	    *archive_name = buf;
	  else
	    free (buf);
	  return WEXITSTATUS (status);
	}

      free (buf);
      return -1;
    }

  /* Child */
  setenv ("TAR_VERSION", PACKAGE_VERSION, 1);
  setenv ("TAR_ARCHIVE", *archive_name, 1);
  setenv ("TAR_VOLUME", STRINGIFY_BIGINT (volume_number, uintbuf), 1);
  setenv ("TAR_BLOCKING_FACTOR",
	  STRINGIFY_BIGINT (blocking_factor, uintbuf), 1);
  setenv ("TAR_SUBCOMMAND", subcommand_string (subcommand_option), 1);
  setenv ("TAR_FORMAT",
	  archive_format_string (current_format == DEFAULT_FORMAT ?
				 archive_format : current_format), 1);
  setenv ("TAR_FD", STRINGIFY_BIGINT (p[PWRITE], uintbuf), 1);

  xclose (p[PREAD]);

  argv[0] = "/bin/sh";
  argv[1] = "-c";
  argv[2] = (char*) info_script_option;
  argv[3] = NULL;

  execv (argv[0], argv);

  exec_fatal (info_script_option);
}

void
sys_exec_checkpoint_script (const char *script_name,
			    const char *archive_name,
			    int checkpoint_number)
{
  pid_t pid;
  char *argv[4];
  char uintbuf[UINTMAX_STRSIZE_BOUND];

  pid = xfork ();

  if (pid != 0)
    {
      /* Master */

      int status;

      while (waitpid (pid, &status, 0) == -1)
	if (errno != EINTR)
	  {
	    waitpid_error (script_name);
	    break;
	  }

      return;
    }

  /* Child */
  setenv ("TAR_VERSION", PACKAGE_VERSION, 1);
  setenv ("TAR_ARCHIVE", archive_name, 1);
  setenv ("TAR_CHECKPOINT", STRINGIFY_BIGINT (checkpoint_number, uintbuf), 1);
  setenv ("TAR_BLOCKING_FACTOR",
	  STRINGIFY_BIGINT (blocking_factor, uintbuf), 1);
  setenv ("TAR_SUBCOMMAND", subcommand_string (subcommand_option), 1);
  setenv ("TAR_FORMAT",
	  archive_format_string (current_format == DEFAULT_FORMAT ?
				 archive_format : current_format), 1);
  argv[0] = "/bin/sh";
  argv[1] = "-c";
  argv[2] = (char*) script_name;
  argv[3] = NULL;

  execv (argv[0], argv);

  exec_fatal (script_name);
}

#endif /* not MSDOS */