問題描述

我正在從 Python 運行一個 C 可執行文件，這個可執行文件有時會出現段錯誤.當它發生段錯誤時，子進程模塊不會在 stdout 或 stderr 中返回任何內容.

I'm running a C executable from Python and this executable sometimes segfaults. When it segfaults the subprocess module does not return anything in stdout or stderr.

示例代碼:

import subprocess

proc = subprocess.Popen(['./a.out'], stdin=subprocess.PIPE,
        stdout=subprocess.PIPE, stderr=subprocess.PIPE)
out, err = proc.communicate()
print 'out: "%s"' % out
print 'err: "%s"' % err
print proc.returncode

a.out的來源是:

int main() {
    printf("hello world
");
    int x = 1 / 0;
}

./a.out的輸出是:

hello world
Floating point exception

Python 代碼的輸出是(在 Linux 中，python 2.7):

The output of the Python code is (in Linux, python 2.7):

out: ""
err: ""
-8

有沒有辦法在可執行文件崩潰的情況下獲取它的輸出?

Is there a way to get the output of the executable even if it crashes?

將返回碼轉換為字符串消息的通用方法也不錯.

A generic method to translate returncode to a string message, would also be nice.

推薦答案

你的 C 程序沒有刷新它的輸出緩沖區.解決此問題的最簡單方法是將 STDOUT 的輸出模式更改為無緩沖:

Your C program is not flushing its output buffer. The easiest way around this problem is to change the output mode of STDOUT to unbuffered:

#include <stdio.h>
int main(int argc,char **argv) {
    setvbuf(stdout,_IONBF,0,0);
    printf("hello world
");
    int x = 1 / 0;
}

現在您的程序(我對其進行了編輯以修復錯字)產生了正確的輸出:

Now your program (which I edited to fix a typo) produces the correct output:

$ python2.7 x.py
out: "hello world
"
err: ""
0
$

在我的 Mac 上返回碼是 0，令人困惑，因為因信號而終止的程序沒有返回碼.

The return code is 0 on my Mac, confusingly, because programs that are terminated for a signal don't have a return code.

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