iwordexp.c

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      *(*expr)++ = 0;

      if (eval_expr (digit, result))
	return WRDE_SYNTAX;

      return 0;

    case '+':	/* Positive value */
      ++digit;
      break;

    case '-':	/* Negative value */
      ++digit;
      sgn = -1;
      break;

    default:
      if (!isdigit (*digit))
	return WRDE_SYNTAX;
    }

  *result = 0;
  for (; *digit && isdigit (*digit); ++digit)
    *result = (*result * 10) + (*digit - '0');

  *expr = digit;
  *result *= sgn;
  return 0;
}

static int
internal_function
eval_expr_multdiv (char **expr, long int *result)
{
  long int arg;

  /* Read a Value */
  if (eval_expr_val (expr, result) != 0)
    return WRDE_SYNTAX;

  while (**expr)
    {
      /* Skip white space */
      for (; *expr && **expr && isspace (**expr); ++(*expr));

      if (**expr == '*')
	{
	  ++(*expr);
	  if (eval_expr_val (expr, &arg) != 0)
	    return WRDE_SYNTAX;

	  *result *= arg;
	}
      else if (**expr == '/')
	{
	  ++(*expr);
	  if (eval_expr_val (expr, &arg) != 0)
	    return WRDE_SYNTAX;

	  *result /= arg;
	}
      else break;
    }

  return 0;
}

static int
internal_function
eval_expr (char *expr, long int *result)
{
  long int arg;

  /* Read a Multdiv */
  if (eval_expr_multdiv (&expr, result) != 0)
    return WRDE_SYNTAX;

  while (*expr)
    {
      /* Skip white space */
      for (; expr && *expr && isspace (*expr); ++expr);

      if (*expr == '+')
	{
	  ++expr;
	  if (eval_expr_multdiv (&expr, &arg) != 0)
	    return WRDE_SYNTAX;

	  *result += arg;
	}
      else if (*expr == '-')
	{
	  ++expr;
	  if (eval_expr_multdiv (&expr, &arg) != 0)
	    return WRDE_SYNTAX;

	  *result -= arg;
	}
      else break;
    }

  return 0;
}

static int
internal_function
parse_arith (char **word, size_t *word_length, size_t *max_length,
	     const char *words, size_t *offset, int flags, int bracket)
{
  /* We are poised just after "$((" or "$[" */
  int error;
  int paren_depth = 1;
  size_t expr_length;
  size_t expr_maxlen;
  char *expr;

  expr = w_newword (&expr_length, &expr_maxlen);
  for (; words[*offset]; ++(*offset))
    {
      switch (words[*offset])
	{
	case '$':
	  error = parse_dollars (&expr, &expr_length, &expr_maxlen,
				 words, offset, flags, NULL, NULL, NULL, 1);
	  /* The ``1'' here is to tell parse_dollars not to
	   * split the fields.
	   */
	  if (error)
	    {
	      free (expr);
	      return error;
	    }
	  break;

	case '`':
	  (*offset)++;
	  error = parse_backtick (&expr, &expr_length, &expr_maxlen,
				  words, offset, flags, NULL, NULL, NULL);
	  /* The first NULL here is to tell parse_backtick not to
	   * split the fields.
	   */
	  if (error)
	    {
	      free (expr);
	      return error;
	    }
	  break;

	case '\\':
	  error = parse_qtd_backslash (&expr, &expr_length, &expr_maxlen,
				       words, offset);
	  if (error)
	    {
	      free (expr);
	      return error;
	    }
	  /* I think that a backslash within an
	   * arithmetic expansion is bound to
	   * cause an error sooner or later anyway though.
	   */
	  break;

	case ')':
	  if (--paren_depth == 0)
	    {
	      char result[21];	/* 21 = ceil(log10(2^64)) + 1 */
	      long int numresult = 0;
	      long long int convertme;

	      if (bracket || words[1 + *offset] != ')')
		{
		  free (expr);
		  return WRDE_SYNTAX;
		}

	      ++(*offset);

	      /* Go - evaluate. */
	      if (*expr && eval_expr (expr, &numresult) != 0)
		{
		  free (expr);
		  return WRDE_SYNTAX;
		}

	      if (numresult < 0)
		{
		  convertme = -numresult;
		  *word = w_addchar (*word, word_length, max_length, '-');
		  if (!*word)
		    {
		      free (expr);
		      return WRDE_NOSPACE;
		    }
		}
	      else
		convertme = numresult;

	      result[20] = '\0';
	      *word = w_addstr (*word, word_length, max_length,
				itoa (convertme, &result[20], 10, 0));
	      free (expr);
	      return *word ? 0 : WRDE_NOSPACE;
	    }
	  expr = w_addchar (expr, &expr_length, &expr_maxlen, words[*offset]);
	  if (expr == NULL)
	    return WRDE_NOSPACE;

	  break;

	case ']':
	  if (bracket && paren_depth == 1)
	    {
	      char result[21];	/* 21 = ceil(log10(2^64)) + 1 */
	      long int numresult = 0;

	      /* Go - evaluate. */
	      if (*expr && eval_expr (expr, &numresult) != 0)
		{
		  free (expr);
		  return WRDE_SYNTAX;
		}

	      result[20] = '\0';
	      *word = w_addstr (*word, word_length, max_length,
				itoa_word (numresult, &result[20], 10, 0));
	      free (expr);
	      return *word ? 0 : WRDE_NOSPACE;
	    }

	  free (expr);
	  return WRDE_SYNTAX;

	case '\n':
	case ';':
	case '{':
	case '}':
	  free (expr);
	  return WRDE_BADCHAR;

	case '(':
	  ++paren_depth;
	default:
	  expr = w_addchar (expr, &expr_length, &expr_maxlen, words[*offset]);
	  if (expr == NULL)
	    return WRDE_NOSPACE;
	}
    }

  /* Premature end */
  free (expr);
  return WRDE_SYNTAX;
}

/* Function called by child process in exec_comm() */
static void
internal_function
exec_comm_child (char *comm, int *fildes, int showerr, int noexec)
{
  const char *args[4] = { "/bin/sh", "-c", comm, NULL };

  /* Execute the command, or just check syntax? */
  if (noexec)
    args[1] = "-nc";

  /* Redirect output.  */
  dup2 (fildes[1], 1);
  close (fildes[1]);

  /* Redirect stderr to /dev/null if we have to.  */
  if (showerr == 0)
    {
      int fd;
      close (2);
      fd = open ("/dev/null", O_WRONLY);
      if (fd >= 0 && fd != 2)
	{
	  dup2 (fd, 2);
	  close (fd);
	}
      }
  /* Make sure the subshell doesn't field-split on our behalf. */
  unsetenv ("IFS");

  close (fildes[0]);
  execve ("/bin/sh", (char *const *) args, environ);

  /* Bad.  What now?  */
  abort ();
}

/* Function to execute a command and retrieve the results */
/* pwordexp contains NULL if field-splitting is forbidden */
static int
internal_function
exec_comm (char *comm, char **word, size_t *word_length, size_t *max_length,
	   int flags, wordexp_t *pwordexp, const char *ifs,
	   const char *ifs_white)
{
  int fildes[2];
  int bufsize = 128;
  int buflen;
  int i;
  int status = 0;
  size_t maxnewlines = 0;
  char *buffer;
  pid_t pid;

  /* Don't fork() unless necessary */
  if (!comm || !*comm)
    return 0;

  if (pipe (fildes))
    /* Bad */
    return WRDE_NOSPACE;

  if ((pid = fork ()) < 0)
    {
      /* Bad */
      close (fildes[0]);
      close (fildes[1]);
      return WRDE_NOSPACE;
    }

  if (pid == 0)
    exec_comm_child(comm, fildes, (flags & WRDE_SHOWERR), 0);

  /* Parent */

  close (fildes[1]);
  buffer = alloca (bufsize);

  if (!pwordexp)
    /* Quoted - no field splitting */
    {
      while (1)
	{
	  if ((buflen = read (fildes[0], buffer, bufsize)) < 1)
	    {
	      if (waitpid (pid, &status, WNOHANG) == 0)
		continue;
	      if ((buflen = read (fildes[0], buffer, bufsize)) < 1)
		break;
	    }

	  maxnewlines += buflen;

	  *word = w_addmem (*word, word_length, max_length, buffer, buflen);
	  if (*word == NULL)
	    goto no_space;
	}
    }
  else
    /* Not quoted - split fields */
    {
      int copying = 0;
      /* 'copying' is:
       *  0 when searching for first character in a field not IFS white space
       *  1 when copying the text of a field
       *  2 when searching for possible non-whitespace IFS
       *  3 when searching for non-newline after copying field
       */

      while (1)
	{
	  if ((buflen = read (fildes[0], buffer, bufsize)) < 1)
	    {
	      if (waitpid (pid, &status, WNOHANG) == 0)
		continue;
	      if ((buflen = read (fildes[0], buffer, bufsize)) < 1)
		break;
	    }

	  for (i = 0; i < buflen; ++i)
	    {
	      if (strchr (ifs, buffer[i]) != NULL)
		{
		  /* Current character is IFS */
		  if (strchr (ifs_white, buffer[i]) == NULL)
		    {
		      /* Current character is IFS but not whitespace */
		      if (copying == 2)
			{
			  /*            current character
			   *                   |
			   *                   V
			   * eg: text<space><comma><space>moretext
			   *
			   * So, strip whitespace IFS (like at the start)
			   */
			  copying = 0;
			  continue;
			}

		      copying = 0;
		      /* fall through and delimit field.. */
		    }
		  else
		    {
		      if (buffer[i] == '\n')
			{
			  /* Current character is (IFS) newline */

			  /* If copying a field, this is the end of it,
			     but maybe all that's left is trailing newlines.
			     So start searching for a non-newline. */
			  if (copying == 1)
			    copying = 3;

			  continue;
			}
		      else
			{
			  /* Current character is IFS white space, but
			     not a newline */

			  /* If not either copying a field or searching
			     for non-newline after a field, ignore it */
			  if (copying != 1 && copying != 3)
			    continue;

			  /* End of field (search for non-ws IFS afterwards) */
			  copying = 2;
			}
		    }

		  /* First IFS white space (non-newline), or IFS non-whitespace.
		   * Delimit the field.  Nulls are converted by w_addword. */
		  if (w_addword (pwordexp, *word) == WRDE_NOSPACE)
		    goto no_space;

		  *word = w_newword (word_length, max_length);

		  maxnewlines = 0;
		  /* fall back round the loop.. */
		}
	      else
		{
		  /* Not IFS character */

		  if (copying == 3)
		    {
		      /* Nothing but (IFS) newlines since the last field,
		         so delimit it here before starting new word */
		      if (w_addword (pwordexp, *word) == WRDE_NOSPACE)
			goto no_space;

		      *word = w_newword (word_length, max_length);
		    }

		  copying = 1;

		  if (buffer[i] == '\n') /* happens if newline not in IFS */
		    maxnewlines++;
		  else
		    maxnewlines = 0;

		  *word = w_addchar (*word, word_length, max_length,
				     buffer[i]);
		  if (*word == NULL)
		    goto no_space;
		}
	    }
	}
    }

  /* Chop off trailing newlines (required by POSIX.2)  */
  /* Ensure we don't go back further than the beginning of the
     substitution (i.e. remove maxnewlines bytes at most) */
  while (maxnewlines-- != 0 &&
         *word_length > 0 && (*word)[*word_length - 1] == '\n')
    {
      (*word)[--*word_length] = '\0';

      /* If the last word was entirely newlines, turn it into a new word
       * which can be ignored if there's nothing following it. */
      if (*word_length == 0)
	{
	  free (*word);
	  *word = w_newword (word_length, max_length);
	  break;
	}
    }

  close (fildes[0]);

  /* Check for syntax error (re-execute but with "-n" flag) */
  if (buflen < 1 && status != 0)
    {
      if ((pid = fork ()) < 0)
	{
	  /* Bad */
	  return WRDE_NOSPACE;
	}

      if (pid == 0)
	{
          fildes[0] = fildes[1] = -1;
	  exec_comm_child(comm, fildes, 0, 1);
	}

      if (waitpid (pid, &status, 0) == pid && status != 0)
	return WRDE_SYNTAX;
    }

  return 0;

no_space:
  kill (pid, SIGKILL);
  waitpid (pid, NULL, 0);
  close (fildes[0]);
  return WRDE_NOSPACE;
}

static int
internal_function
parse_comm (char **word, size_t *word_length, size_t *max_length,
	    const char *words, size_t *offset, int flags, wordexp_t *pwordexp,
	    const char *ifs, const char *ifs_white)
{
  /* We are poised just after "$(" */
  int paren_depth = 1;
  int error = 0;
  int quoted = 0; /* 1 for singly-quoted, 2 for doubly-quoted */
  size_t comm_length;
  size_t comm_maxlen;
  char *comm = w_newword (&comm_length, &comm_maxlen);

  for (; words[*offset]; ++(*offset))
    {
      switch (words[*offset])
	{
	case '\'':
	  if (quoted == 0)
	    quoted = 1;
	  else if (quoted == 1)
	    quoted = 0;

	  break;

	case '"':
	  if (quoted == 0)
	    quoted = 2;
	  else if (quoted == 2)
	    quoted = 0;

	  break;

	case ')':
	  if (!quoted && --paren_depth == 0)
	    {
	      /* Go -- give script to the shell */
	      if (comm)
		{
		  error = exec_comm (comm, word, word_length, max_length,
				     flags, pwordexp, ifs, ifs_white);
		  free (comm);
		}

	      return error;
	    }

	  /* This is just part of the script */
	  break;

	case '(':
	  if (!quoted)
	    ++paren_depth;
	}

      comm = w_addchar (comm, &comm_length, &comm_maxlen, words[*offset]);
      if (comm == NULL)
	return WRDE_NOSPACE;
    }

  /* Premature end */
  if (comm)
    free (comm);

  return WRDE_SYNTAX;
}

static int
internal_function
parse_param (char **word, size_t *word_length, size_t *max_length,
	     const char *words, size_t *offset, int flags, wordexp_t *pwordexp,
	     const char *ifs, const char *ifs_white, int quoted)
{
  /* We are poised just after "$" */
  enum action
  {
    ACT_NONE,
    ACT_RP_SHORT_LEFT = '#',
    ACT_RP_LONG_LEFT = 'L',
    ACT_RP_SHORT_RIGHT = '%',
    ACT_RP_LONG_RIGHT = 'R',
    ACT_NULL_ERROR = '?',
    ACT_NULL_SUBST = '-',
    ACT_NONNULL_SUBST = '+',
    ACT_NULL_ASSIGN = '='
  };
  size_t env_length;