无法使用Runtime.exec()在Android Java代码中执行shell命令"echo"

Question

我可以Runtime.exec()用来执行像" getprop"和" ls system" 这样的shell命令,它们工作正常.

但是,当我使用" echo $BOOTCLASSPATH"," echo \\$BOOTCLASSPATH"或" echo HelloWorld"时,它不会在stdout中显示它.

logcat显示:

I/AndroidRuntime( 4453): VM exiting with result code -1.

这是我的代码:

try {
    java.lang.Process proc = Runtime.getRuntime().exec("echo -e \\$BOOTCLASSPATH");
    String line = null;

    InputStream stderr = proc.getErrorStream();
    InputStreamReader esr = new InputStreamReader (stderr);
    BufferedReader ebr = new BufferedReader (esr);
    while ( (line = ebr.readLine()) != null )
        Log.e("FXN-BOOTCLASSPATH", line);

    InputStream stdout = proc.getInputStream();
    InputStreamReader osr = new InputStreamReader (stdout);
    BufferedReader obr = new BufferedReader (osr);
    while ( (line = obr.readLine()) != null )
        Log.i("FXN-BOOTCLASSPATH", line);

    int exitVal = proc.waitFor();
    Log.d("FXN-BOOTCLASSPATH", "getprop exitValue: " + exitVal);
} catch (Exception e) {
    e.printStackTrace();
}

Answer 1

@Adi Tiwari,我找到了原因. Runtime.getRuntime.exec()不直接执行shell命令,它使用参数执行可执行文件." echo"是内置的shell命令.它实际上是sh带有该选项的可执行文件参数的一部分-c.命令就像ls是实际的可执行文件.您可以使用type echo和type ls命令adb shell查看差异.
所以最终的代码是:

String[] cmdline = { "sh", "-c", "echo $BOOTCLASSPATH" }; 
Runtime.getRuntime().exec(cmdline);