Difference between windows and linux with double quotes

[Carl Saint]

Hi,

I am hitting an issue or difference in behaviour when running picocli on windows and linux.

If the command line has something like -

 --json='{"name": "value"}'

parsed on windows - {name: value}

parsed on linux - {"name": "value"}

picocli strips out the double quotes on windows but leaves them on linux (the desired behaviour).

I have switched on picocli debug and see the following debug, which shows the difference when run on windows and on linux

[picocli INFO] Parsing 12 command line args ... 

Am i missing something obvious?

I am using cygwin shell on windows, bash shell on linux. 

I am using picocli 4.5.2

Thanks for any help

Carl

[Carl Saint]

The code below shows the different output when run on either linux or windows. I need to preserve the quotes for valid JSON

Code:

------------

/*

 * This Java source file was generated by the Gradle 'init' task.

 */

package picocli.demo;

import java.util.concurrent.Callable;

import picocli.CommandLine;

import picocli.CommandLine.Option;

public class App implements Callable<Integer>

{

    @Option(names="--json", description="valid json")

    String json;

    @Override

    public Integer call() throws Exception { // your business logic goes here...

        System.out.println("JSON - "+json);

        return 0;

    }

    public static void main(String[] args)

    {  

        int exitCode = new CommandLine(new App()).execute(args);

        System.out.println("Exitcode - "+exitCode);

    }

}

--------------

Linux:

# java -jar picocli-demo.jar --json='{ "name": "value" }'

JSON - { "name": "value" }

Exitcode - 0

Windows:

$ java -jar picocli-demo.jar --json='{ "name": "value" }'

JSON - { name: value }

Exitcode - 0

[Remko Popma]

I am getting slightly different results on Windows (see below), but it looks like two things are happening on the Windows Command Prompt shell:

• the CMD shell strips out double quotes
• single quotes do not have special meaning in the command prompt shell: 'a b' is interpreted by the shell as two arguments: ['a] and [b']

I modified your program a bit to also print the raw args as they are passed by the command prompt shell to the Java process:

public class QuotingDemo implements Runnable {
  @Option(names = "--json", description = "valid json")
  String json;

  @Override
  public void run() {
    System.out.println("JSON - " + json);

  }

  public static void main(String[] args) {

    System.out.println("Args=" + Arrays.toString(args));
    int exitCode = new CommandLine(new QuotingDemo()).execute(args);

    System.out.println("Exitcode - " + exitCode);
  }
}

On the Windows command prompt, I see this:

java -cp "c:\Users\remko\picocli-4.5.2.jar;." QuotingDemo --json='{"name": "value"}'

Args=[--json='{name:, value}']

Unmatched argument at index 1: 'value}''

Usage: <main class> [--json=<json>]

      --json=<json>   valid json

Exitcode - 2

Note that the raw args no longer contain double quotes, and the args array contains two elements: the first is --json='{name:, and the second is value}'.

Picocli then shows an error for the second argument (value}').

So, on the Windows command prompt, users can only quote using double quotes.

When the option parameter is quoted with double quotes in CMD prompt, the Java process receives a single argument (as intended):

java -cp "c:\Users\remko\picocli-4.5.2.jar;." QuotingDemo --json="{'name': 'value'}"

Args=[--json={'name': 'value'}]

JSON - {'name': 'value'}

Exitcode - 0

This SO question/answer may be useful: https://stackoverflow.com/questions/24173825/what-does-single-quoting-do-in-windows-batch-files

Note that PowerShell has different quoting rules than CMD prompt: https://stackoverflow.com/a/63627261/1446916

The linux shell is more powerful and allows quoting with both single and double quotes.

On linux I see single quotes work as intended: the raw args array contains a single element:

java -cp /mnt/c/Users/remko/picocli-4.5.2.jar:. QuotingDemo --json='{"name": "value"}'

Args=[--json={"name": "value"}]

JSON - {"name": "value"}

Exitcode - 0

Similarly when the option parameter is quoted with double quotes:

java -cp /mnt/c/Users/remko/picocli-4.5.2.jar:. QuotingDemo --json="{'name': 'value'}"

Args=[--json={'name': 'value'}]

JSON - {'name': 'value'}

Exitcode - 0

[Remko Popma]

I just saw you mentioned using cygwin on Windows.

The cygwin bash shell seems to work similar as Linux for me: both double quotes and single quotes are respected.

The following output is from Cygwin (with mintty 2.9.0):

$ java -cp "picocli-4.5.2.jar;." QuotingDemo --json='{"name": "value"}'

Args=[--json={"name": "value"}]

JSON - {"name": "value"}

Exitcode - 0

$ java -cp "picocli-4.5.2.jar;." QuotingDemo --json="{'name': 'value'}"

Args=[--json={'name': 'value'}]

JSON - {'name': 'value'}

Exitcode - 0

[Carl Saint]

Thanks for your reply. It does just seem to be a shell difference. I could not get the cygwin to work as you showed above, but it works when i escape the quotes when using cygwin terminal on windows -

$ java  -jar picocli-demo.jar --json='{ \"name\": \"value\" }' 

Args=[--json={ "name": "value" }]

JSON - { "name": "value" }

Exitcode - 0

Many thanks