如何从Java调用Linux Shell命令

Question 1

我正在尝试使用重定向（>＆）和管道（|）从Java执行一些Linux命令。Java如何调用csh或bash命令？

我试图用这个：

Process p = Runtime.getRuntime().exec("shell command");

但这与重定向或管道不兼容。

Question 2

exec在您的shell中不执行命令

尝试

Process p = Runtime.getRuntime().exec(new String[]{"csh","-c","cat /home/narek/pk.txt"});

代替。

编辑：：我的系统上没有csh，所以我改用bash。以下为我工作

Process p = Runtime.getRuntime().exec(new String[]{"bash","-c","ls /home/XXX"});

Question 3

使用ProcessBuilder分隔命令和参数而不是空格。无论使用哪种外壳，这都应该起作用：

import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;

public class Test {

    public static void main(final String[] args) throws IOException, InterruptedException {
        //Build command 
        List<String> commands = new ArrayList<String>();
        commands.add("/bin/cat");
        //Add arguments
        commands.add("/home/narek/pk.txt");
        System.out.println(commands);

        //Run macro on target
        ProcessBuilder pb = new ProcessBuilder(commands);
        pb.directory(new File("/home/narek"));
        pb.redirectErrorStream(true);
        Process process = pb.start();

        //Read output
        StringBuilder out = new StringBuilder();
        BufferedReader br = new BufferedReader(new InputStreamReader(process.getInputStream()));
        String line = null, previous = null;
        while ((line = br.readLine()) != null)
            if (!line.equals(previous)) {
                previous = line;
                out.append(line).append('\n');
                System.out.println(line);
            }

        //Check result
        if (process.waitFor() == 0) {
            System.out.println("Success!");
            System.exit(0);
        }

        //Abnormal termination: Log command parameters and output and throw ExecutionException
        System.err.println(commands);
        System.err.println(out.toString());
        System.exit(1);
    }
}

Question 4

在@Tim的示例上构建一个独立的方法：

import java.io.BufferedReader;
import java.io.File;
import java.io.InputStreamReader;
import java.util.ArrayList;

public class Shell {

    /** Returns null if it failed for some reason.
     */
    public static ArrayList<String> command(final String cmdline,
    final String directory) {
        try {
            Process process = 
                new ProcessBuilder(new String[] {"bash", "-c", cmdline})
                    .redirectErrorStream(true)
                    .directory(new File(directory))
                    .start();

            ArrayList<String> output = new ArrayList<String>();
            BufferedReader br = new BufferedReader(
                new InputStreamReader(process.getInputStream()));
            String line = null;
            while ( (line = br.readLine()) != null )
                output.add(line);

            //There should really be a timeout here.
            if (0 != process.waitFor())
                return null;

            return output;

        } catch (Exception e) {
            //Warning: doing this is no good in high quality applications.
            //Instead, present appropriate error messages to the user.
            //But it's perfectly fine for prototyping.

            return null;
        }
    }

    public static void main(String[] args) {
        test("which bash");

        test("find . -type f -printf '%T@\\\\t%p\\\\n' "
            + "| sort -n | cut -f 2- | "
            + "sed -e 's/ /\\\\\\\\ /g' | xargs ls -halt");

    }

    static void test(String cmdline) {
        ArrayList<String> output = command(cmdline, ".");
        if (null == output)
            System.out.println("\n\n\t\tCOMMAND FAILED: " + cmdline);
        else
            for (String line : output)
                System.out.println(line);

    }
}

（测试示例是命令，命令按时间顺序递归列出目录及其子目录中的所有文件。）

顺便说一句，如果有人可以告诉我为什么我在那里需要四个和八个反斜杠，而不是两个和四个，我可以学到一些东西。比我所计数的还要多的一种无法逃避的事情正在发生。

编辑：刚刚在Linux上尝试过相同的代码，结果发现我在test命令中需要一半的反斜杠！（即：预期的2和4。）现在，它不再只是怪异的，而是可移植性问题。