在程序中调用外部程序，用process返回命令执行结果以及抓取错误信息的方法

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在Java中，通过`Runtime.getRuntime().exec()`方法可以创建一个子进程来执行外部程序，如ksh。使用`Process`对象的`waitFor()`方法等待外部程序完成并获取其退出状态码，这通常用于判断程序是否正常结束。当需要捕获外部程序的输出或错误信息时，可以分别读取`getInputStream()`和`getErrorStream()`，以便分析和处理可能出现的问题。

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在Java代码里调用外部程序时，比如一个ksh等，可以用如下方法：

The ProcessBuilder.start() and Runtime.exec methods create a native process and return an instance of a subclass of Process that can be used to control the process and obtain information about it.

所以在调用外部程序时，使用process将启动一个新进程，用于执行外部程序。使用waitfor()等待外部程序执行完毕并返回值。

String command = String.format(CHECK_GRAPH_IS_RUNNING_FORMAT, recoveryFile.getAbsolutePath());
Process process = execCommand(command);

int isRunningExitCode = process.waitFor();

return (SUCCESS_EXIT_VALUE == isRunningExitCode);

protected Process execCommand(final String command) throws IOException {
return Runtime.getRuntime().exec(command, getEnvp(), getWorkingFolder());
}

process.waitFor();

causes the current thread to wait, if necessary, until the process represented by this Process object has terminated. This method returns immediately if the subprocess has already terminated. If the subprocess has not yet terminated, the calling thread will be blocked until the subprocess exits.

the exit value of the process. By convention, 0 indicates normal termination.

返回的这个参数isRunningExitCode 就是command运行的返回值。

此外，当运行外部程序出现错误时，可以很方便的抓取返回信息并进一步加以分析。

private Process process;

process = launchTaskProcess();

processOutStreamLog = process == null ? EMPTY : NEW_LINE + "Task process out stream >>>> " + NEW_LINE
+ readInputStream(process.getInputStream());

processErrorStreamLog = process == null ? EMPTY : NEW_LINE + "Task process error stream >>>> "
+ NEW_LINE + readInputStream(process.getErrorStream());

这里的process.getInputStream() 和 process.getErrorStream() 就可以取得执行的process的outputmessage.