java编写shell命令解析规则

因业务需求，要对shell命令添加一个白名单，因此需要对shell进行一个简单的解析，代码跑了两天基本满足现阶段要求，代码如下：

public static void main(String[] args) {
		System.out.println(checkCmd("zgrep oHQwN0ZYayuTyNZHAosTKc7uP6vk $logpath | grep -o \"cmd=[^ ]*\" | sort | uniq -c".trim()));
	}

    public static boolean checkCmd(String grep) {
		List<List<String>> unitList = new ArrayList<>();
		List<String> tokenList = new ArrayList<>();
		boolean flag = false;
		char punc = '~';
		StringBuilder sb = new StringBuilder();
		int pre = 0, i;
		for (i = 0; i < grep.length() && pre < grep.length(); i++) {
			char c = grep.charAt(i);
			if (flag) {
				if (c == punc) {
					flag = false;
					tokenList.add(grep.substring(pre + 1, i));
					pre = i + 1;
				}
			} else {
				if (c == ' ' || c == '|') {
					tokenList.add(grep.substring(pre, i));
					pre = i + 1;
					if (c == '|') {
						unitList.add(new ArrayList<>(tokenList));
						tokenList.clear();
					}
				} else if ((c == '\'' || c == '"') && !flag) {
					flag = true;
					punc = c;
				}
			}
		}
		if (pre < grep.length()) {
			tokenList.add(grep.substring(pre, i));
			unitList.add(new ArrayList<>(tokenList));
		}
		//拿到白名单
		List<String> wightTokenList = Utils.getTokenWightList();
		for (List<String> list : unitList) {
			List<String> tokens = list.stream().filter(s -> !s.trim().equals("")).collect(Collectors.toList());
			if (!wightTokenList.contains(tokens.get(0)) || !legalPath(tokens)) {
				return false;
			}
		}
		return true;
    }

	private static boolean legalPath(List<String> tokens) {
		if (tokens.get(0).equals("less") || tokens.get(0).equals("cat") || tokens.get(0).equals("nl")) {
			String last = tokens.get(tokens.size() - 1);
			if (last.indexOf("/") > -1) {
				return false;
			}
		}
		return true;
	}