从Java程序调用命令历史记录

Question

我们试图从Java程序调用Linux命令history。我们能够从Java调用相当多的命令，包括date和ls-l而没有任何问题。但是，historyjava.io.ioException失败。示例源代码如下：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

public class OSCommand {
    public static void main(String[] args) throws Exception {
        dumpCommandOutput("Date", new String[] {"date"});
        // SUCCEEDS

        dumpCommandOutput("Long Directory Listing", new String[] {"ls", "-l"});
        // SUCCEEDS

        dumpCommandOutput("Command History", new String[] {"history"});
        // FAILS
    }

    protected static void dumpCommandOutput(String label, String[] cmdWithArgs) throws IOException {
        System.out.println("Attempting to execute: " + label);
        
        Process p = Runtime.getRuntime().exec(cmdWithArgs);

        InputStream is = p.getInputStream();
        BufferedReader br = new BufferedReader(new InputStreamReader(is));
        
        String str;
        
        while((str = br.readLine()) != null) {
            System.out.println(str);
        }
        br.close();
        System.out.println("\n\n");
    }
}

引发的异常

Exception in thread "main" java.io.IOException: Cannot run program "history": error=2, No such file or directory
        at java.lang.ProcessBuilder.start(ProcessBuilder.java:1048)
        at java.lang.Runtime.exec(Runtime.java:621)
        at java.lang.Runtime.exec(Runtime.java:486)
        at OSCommand.dumpCommandOutput(OSCommand.java:16)
        at OSCommand.main(OSCommand.java:10)
Caused by: java.io.IOException: error=2, No such file or directory
        at java.lang.UNIXProcess.forkAndExec(Native Method)
        at java.lang.UNIXProcess.<init>(UNIXProcess.java:247)
        at java.lang.ProcessImpl.start(ProcessImpl.java:134)
        at java.lang.ProcessBuilder.start(ProcessBuilder.java:1029)
        ... 4 more

Answer 1

命令“history”不是linux发行版中已安装的程序。相反，它是您正在使用的shell中提供的内置命令。因此，java不需要使用runtime.getruntime().exec()来执行。检查对date、ls和history的参数使用whice命令时得到的结果：

linryzen ~ # echo $0
bash
linryzen ~ # which ls
/bin/ls
linryzen ~ # which date
/bin/date
linryzen ~ # which history
which: no history in (/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:
                      /opt/bin:/usr/lib/llvm/12/bin:/usr/lib/llvm/11/bin:
                      /usr/lib/llvm/9/bin)
linryzen ~ #