Question

我在String变量中有一个Rscript，我想从Java程序执行它并将一些变量传递给它。如果我独立执行该R脚本，它可以正常工作。我已经通过使用Python程序将其转换为一行来将该R脚本转换为一行，如下所示：

import json

jsonstr = json.dumps({"script": """\
#!/usr/bin/Rscript

# read the data file
library('jsonlite')
library('rpart')

args <- as.list(Sys.getenv(c(
                        "path",
                        "client_users")))

if (args[["path"]]==""){
    args[["path"]] <- "."
}

# other stuff here
# other stuff here

"""})

print jsonstr

我使用打印出的字符串并将其存储在String变量中，然后我使用下面的代码执行它根本不起作用。我将path和client_users变量传递给上面的R脚本。

public static void main(String[] args) throws IOException, InterruptedException {

    // this is your script in a string
    // String script = "#!/bin/bash\n\necho \"Hello World\"\n\n readonly PARAM1=$param1\n echo $PARAM1\n\nreadonly PARAM2=$param2\n echo $PARAM2\n\n";
    String script = "above R Script here";

    List<String> commandList = new ArrayList<>();
    commandList.add("/bin/bash");

    ProcessBuilder builder = new ProcessBuilder(commandList);
    builder.environment().put("path", "/home/david");
    builder.environment().put("client_users", "1000");
    builder.redirectErrorStream(true);
    Process shell = builder.start();

    // Send your script to the input of the shell, something
    // like doing cat script.sh | bash in the terminal
    try(OutputStream commands = shell.getOutputStream()) {
        commands.write(script.getBytes());
    }

    // read the outcome
    try(BufferedReader reader = new BufferedReader(new InputStreamReader(shell.getInputStream()))) {
        String line;
        while((line = reader.readLine()) != null) {
            System.out.println(line);
        }
    }

    // check the exit code
    int exitCode = shell.waitFor();
    System.out.println("EXIT CODE: " + exitCode);
}

上面的代码适用于bash shell脚本。我需要为R脚本做些什么特别的事吗？我将使用相同的代码来处理bash脚本和R脚本。

这是我得到的错误：

/bin/bash: line 7: -: No such file or directory /bin/bash: line 10: syntax error near unexpected token `'jsonlite'' /bin/bash: line 10: `library('jsonlite')'

如果我删除commandList.add("/bin/bash");并添加commandList.add("/bin/Rscript");，那么我会看到以下错误：

Cannot run program "/bin/Rscript": error=2, No such file or directory

更新： -

我没有使用上面的脚本，而是决定在r中使用简单的打印地狱脚本来查看是否可以通过Java执行它。

// this will print hello
String script = "#!/usr/bin/env Rscript\nsayHello <- function(){\n   print('hello')\n}\n\nsayHello()\n";

当我使用commandList.add("/bin/bash");执行此脚本时，出现此错误：

/bin/bash: line 2: syntax error near unexpected token `('
/bin/bash: line 2: `sayHello <- function(){'

但如果我执行此commandList.add("/bin/sh");，我会收到此错误：

/bin/sh: 2: Syntax error: "(" unexpected

Answer 1

您必须直接运行/usr/bin/Rscript。此外，此程序不读取标准输入中的脚本（您必须指定脚本的路径作为Rscript的参数），因此您必须：

创建临时文件
编写脚本
使用Rscript
删除临时文件（作为一种优秀的编程习惯）

例如，这是一个POC：

public static void main(String[] args) throws IOException, InterruptedException {

    // Your script
    String script = "#!/usr/bin/env Rscript\n" +
            "\n" +
            "sayHello <- function() {\n" +
            "    print('hello')\n" +
            "}\n" +
            "\n" +
            "sayHello()\n";

    // create a temp file and write your script to it
    File tempScript = File.createTempFile("test_r_scripts_", "");
    try(OutputStream output = new FileOutputStream(tempScript)) {
        output.write(script.getBytes());
    }

    // build the process object and start it
    List<String> commandList = new ArrayList<>();
    commandList.add("/usr/bin/Rscript");
    commandList.add(tempScript.getAbsolutePath());
    ProcessBuilder builder = new ProcessBuilder(commandList);
    builder.redirectErrorStream(true);
    Process shell = builder.start();

    // read the output and show it
    try(BufferedReader reader = new BufferedReader(
            new InputStreamReader(shell.getInputStream()))) {
        String line;
        while((line = reader.readLine()) != null) {
            System.out.println(line);
        }
    }

    // wait for the process to finish
    int exitCode = shell.waitFor();

    // delete your temp file
    tempScript.delete();

    // check the exit code (exit code = 0 usually means "executed ok")
    System.out.println("EXIT CODE: " + exitCode);
}

作为替代方案，如果您的脚本有“shebang”作为第一行，您可以执行以下更改：

将其可执行属性设置为“true”
使用临时文件的路径作为commandList中的第一个元素（即删除commandList.add("/usr/bin/Rscript");）

要修改的代码部分是：

...

// create a temp file and write your script to it
File tempScript = File.createTempFile("test_r_scripts_", "");
tempScript.setExecutable(true);
try(OutputStream output = new FileOutputStream(tempScript)) {
    output.write(script.getBytes());
}

// build the process object and start it
List<String> commandList = new ArrayList<>();
commandList.add(tempScript.getAbsolutePath());
ProcessBuilder builder = new ProcessBuilder(commandList);

...

无法从java程序执行R脚本？

1 个答案: