我正在尝试将sam-ba.exe的输出（通过USB将代码加载到ARM微控制器）读入Java程序。在命令提示符下编写此确切命令时：
"sam-ba_3.2.1\sam-ba.exe" -p usb -d SAME70 -a internalflash
结果是：
Error: No serial ports found
但是在以下Java代码中执行此命令时，标准输出或标准错误流均不返回任何内容（请参见以下内容）：
Command executed: "sam-ba_3.2.1\sam-ba.exe" -p usb -d SAME70 -a internalflash
Here is the standard output of the command:
Here is the standard error of the command (if any):
更令人讨厌的是，用Java代码替换此命令将在stderr流中返回信息：
"sam-ba_3.2.1\sam-ba.exe" --help
结果：
Here is the standard output of the command:
Here is the standard error of the command (if any):
SAM-BA Command Line Tool v3.2.1
Copyright 2015-2017 ATMEL Corporation
Usage: sam-ba_3.2.1\sam-ba.exe [options]
Options:
-v, --version Displays version information.
-h, --help Displays this help.
-t, --tracelevel <trace_level> Set trace level to <trace_level>.
-x, --execute <script.qml> Execute script <script-file>.
-p, --port <port[:options:...]> Communicate with device using <port>.
-d, --device <device[:options:...]> Connected device is <device>.
-b, --board <board[:options:...]> Connected board is <board>.
-m, --monitor <command[:options:...]> Run monitor command <command>.
-a, --applet <applet[:options:...]> Load and initialize applet <applet>.
-c, --command <command[:args:...]> Run command <command>.
在控制台中，我尝试将第一个（非工作）命令的输出重定向到文本文件，并且该文本文件显示预期的错误，无串行端口，但仅在使用以下命令时显示：
"sam-ba_3.2.1\sam-ba.exe" -p usb -d SAME70 -a internalflash > output.txt 2>&1
这使我相信该消息来自stderr，因为如果我省略“ 2>＆1”，则文本文件为空白。但是，为什么Java程序中的stderr空白？
这是我的Java代码：
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.InputStream;
import java.io.BufferedReader;
public class ProcessDemo {
public static void main(String[] args) {
try
{
Runtime r = Runtime.getRuntime();
//String command = "\"sam-ba_3.2.1\\sam-ba.exe\" --help";
String command = "\"sam-ba_3.2.1\\sam-ba.exe\" -p usb -d SAME70 -a internalflash";
System.out.println("Command executed: " + command);
Process proc = r.exec(command);
BufferedReader stdInput = new BufferedReader(new InputStreamReader(proc.getInputStream()));
BufferedReader stdError = new BufferedReader(new InputStreamReader(proc.getErrorStream()));
// read the output from the command
System.out.println("Here is the standard output of the command:\n");
String s = null;
while ((s = stdInput.readLine()) != null) {
System.out.println(s);
}
// read any errors from the attempted command
System.out.println("Here is the standard error of the command (if any):\n");
while ((s = stdError.readLine()) != null) {
System.out.println(s);
}
}
catch (Exception e)
{
e.printStackTrace();
}
}
}
任何帮助都会很棒，
贾德
更新：如建议的那样，我现在使用ProcessBuilder并删除了引号，但结果完全相同。
有人建议添加Redirect.INHERIT，如图所示，但会产生以下输出。看起来它只是绕过输入流而直接进入终端？
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.BufferedReader;
public class ProcessDemo {
public static void main(String[] args) {
try
{
// String[] command = {"sam-ba_3.2.1\\sam-ba.exe","--help"};
String[] command = {"sam-ba_3.2.1\\sam-ba.exe", "-p", "usb", "-d", "SAME70", "-a", "internalflash", "-c", "write:\"GCCBoardProject1.bin\""};
ProcessBuilder pb = new ProcessBuilder(command);
pb.redirectOutput(ProcessBuilder.Redirect.INHERIT);
pb.redirectError(ProcessBuilder.Redirect.INHERIT);
Process proc = pb.start();
proc.waitFor();
BufferedReader stdInput = new BufferedReader(new InputStreamReader(proc.getInputStream()));
BufferedReader stdError = new BufferedReader(new InputStreamReader(proc.getErrorStream()));
System.out.println("Here is the standard output of the command:\n");
// read the output from the command
String s = null;
while ((s = stdInput.readLine()) != null)
{
System.out.println(s);
}
// read any errors from the attempted command
System.out.println("Here is the standard error of the command (if any):\n");
while ((s = stdError.readLine()) != null)
{
System.out.println(s);
}
System.out.println("return value: " + proc.exitValue());
}
catch (Exception e)
{
e.printStackTrace();
}
}
}
输出：
Error: No serial ports found
Here is the standard output of the command:
Here is the standard error of the command (if any):
return value: -1
答案 0 :(得分：0)
proc.waitFor（）;该语句应出现在BufferedReader语句之前，并在输入流阅读器中按原样传递。注意：Process.waitFor（）方法暂停当前线程，直到您的进程有机会完成。然后，使用BufferReader可以读取输出。
答案 1 :(得分：0)
当我在程序的进程命令行args中使用mysqld start时，问题似乎是您传递的命令。我能够看到输出。所以问题在于您传递的CLI命令。建议手动运行它，然后查看输出结果。
String[] command = {"C:\\Users\\userid\\Downloads\\mysql-5.7.13-winx64\\mysql-5.7.13-winx64\\bin\\mysqld.exe", "--console"};
样本输出：
C:\Users\userid\other\stk-overflow>java ProcessDemo
2019-05-13T00:57:04.191518Z 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
2019-05-13T00:57:04.191518Z 0 [Warning] 'NO_AUTO_CREATE_USER' sql mode was not set.
2019-05-13T00:57:04.191518Z 0 [Warning] Insecure configuration for --secure-file-priv: Current value does not restrict location of generated files. Consider setting it to a valid, non-empty path.
2019-05-13T00:57:04.191518Z 0 [Note] C:\Users\userid\Downloads\mysql-5.7.13-winx64\mysql-5.7.13-winx64\bin\mysqld.exe (mysqld 5.7.13) starting as process 21604 ...
2019-05-13T00:57:04.201520Z 0 [Note] InnoDB: Mutexes and rw_locks use Windows interlocked functions
2019-05-13T00:57:04.202742Z 0 [Note] InnoDB: Uses event mutexes
2019-05-13T00:57:04.203516Z 0 [Note] InnoDB: _mm_lfence() and _mm_sfence() are used for memory barrier
2019-05-13T00:57:04.203516Z 0 [Note] InnoDB: Compressed tables use zlib 1.2.3
2019-05-13T00:57:04.204517Z 0 [Note] InnoDB: Number of pools: 1
2019-05-13T00:57:04.205519Z 0 [Note] InnoDB: Not using CPU crc32 instructions
2019-05-13T00:57:04.209518Z 0 [Note] InnoDB: Initializing buffer pool, total size = 128M, instances = 1, chunk size = 128M