在Java中拆分命令行

Question

What's the recommended way to parse a shell-like command line in Java. By that I don't mean processing the options when they are already in array form (eg handling "-x" and such), there are loads of questions and answers about that already.

No, I mean the splitting of a full command string into "tokens". I need to convert a string such as:

user 123712378 suspend "They are \"bad guys\"" Or\ are\ they?

...to the list/array:

user
123712378
suspend
They are "bad guys"
Or are they?

I'm currently just doing a split on whitespace, but that obviously can't handle the quotes and escaped spaces.

(Quote handling is most important. Escaped spaces would be nice-to-have)

Note: My command string is the input from a shell-like web interface. It's not built from main(String[] args)

Answer 1

What you would need is to implement a finite automaton. You would need to read the string character by character and find the next state depending on your next or previous character.
For example a " indicates start of a string but if it is preceded by an \\ leaves the current state unchanged and reads until the next token that takes you to the next state.
Ie essentially in your example you would have

read string -> read number   
      ^  -    -   -  |  

You of course would need to define all the states and the special characters that affect or not affect your state.
To be honest I am not sure why you would want to provide such functionality to the end user.
Traditionally all the cli programs accept input in a standard format -x or --x or --x=s etc.
This format is well known to a typical user and is simple to implement and test as correct.
Traditionally if we are required to provide more "flexible" input for the user, it is best to build a GUI. That is what I would suggest.

Answer 2

ArgumentTokenizer from DrJava parses command line in a way Bourne shell and its derivatives do .

It properly supports escapes, so bash -c 'echo "\\"escaped '\\''single'\\'' quote\\""' gets tokenized into [bash, -c, echo "\\"escaped 'single' quote\\""] .

Answer 3

Build the args[] back into a string, then tokenize using regexp:

public static void main(String[] args) {
    String commandline = "";
    for(String arg : args) {
        commandline += arg;
        commandline += " ";
    }
    System.out.println(commandline);

    List<String> list = new ArrayList<String>();
    Matcher m = Pattern.compile("([^\"]\\S*|\".+?\")\\s*").matcher(commandline);
    while (m.find())
        list.add(m.group(1)); // Add .replace("\"", "") to remove surrounding quotes.


    System.out.println(list);
}

The latter part I took from here .