Java Runtime.exec escaped arguments in string

Question

Due to working through a framework, I only have control over the command string of Runtime.getRuntime().exec(string), so no array.

Problem is, I need to pass some escaped arguments and it just doesn't seem to work.

Take this for example: wget -qO- --post-data "<?xml version=\"1.0\" encoding=\"UTF-8\"?><Devices><Device><FLOWCTRL>2</FLOWCTRL></Device></Devices>" -- http://192.168.3.33/data/changes.xml. Works perfectly fine in the shell, but something is messed up since I don't get the proper response (most probably because the data isn't valid).

Edit: https://github.com/openhab/openhab-addons/blob/2.5.x/bundles/org.openhab.binding.exec/src/main/java/org/openhab/binding/exec/internal/handler/ExecHandler.java#L174 Link to code

• azro: could share the code that runs the command ? to see how you pass the string
• MadProgrammer: So, this would be a little messy to continue down the path you've started, a possibly better solution would be to use ProcessBuilder which may reduce the need to quote any of the parameters at all
• Consti P: @MadProgrammer As I said, I have no control over this... I need to do it in one string :(
• dan1st: The shell may support quoting. You could use something like bash -c 'wget ... "..." ...'.
• dan1st: And why can't you use ProcessBuilder? You call getRuntime by yourself. What frameworks prevents that?

Answer 1

As I said, I have no control over this... I need to do it in one string :(

There is no direct solution given that constraint. Period.

It is a plain fact that exec(String) does not understand any form of escaping or quoting. It splits the string into a command name and multiple arguments using whitespace characters as the argument separator. The behavior is hard-wired ... and documented.

---

The possible solutions are:

• Do the splitting yourself, and use exec(String[]).

• Get a shell to do the splitting; e.g.

  String cmd = "wget -qO- --post-data \"<?xml version=\\"1.0\\" ...."
  Runtime.getRuntime().exec("/bin/sh", "-c", cmd);
  

  Note that we are using exec(String[]) here too.

• Generate and run a shell script on the fly:

  1. Write the following script to a temporary file (say "/tmp/abc.sh")

     #!/bin/sh
     wget -qO- --post-data \
      "<?xml version=\"1.0\" encoding=\"UTF-8\"?><Devices><Device><FLOWCTRL>2</FLOWCTRL></Device></Devices>" \
      -- http://192.168.3.33/data/changes.xml
     

  2. Make the script executable

  3. Run it:

      Runtime.getRuntime().exec("/tmp/abc.sh");
     

• Consti P: Sadly I have to send different data. I also don't have control over the exec parameters, so no chance of the first two options. Seems I can only try to write a script that generates the data without having to use spaces... Thanks!