Python 错误代码被调高

Question

考虑一个 python 脚本 error.py

import sys
sys.exit(3)

调用

python error.py; echo $?

产生预期的“3”。但是，请考虑 runner.py

import os
result = os.system("python error.py")
print result

yields 768。python代码的结果好像不知何故左移了8位，但这两种情况有何不同就不清楚了。怎么回事？

这发生在 python 2.5 和 2.6 中。

Answer 1

来自docs :

On Unix, the return value is the exit status of the process encoded in the format specified for wait(). Note that POSIX does not specify the meaning of the return value of the C system() function, so the return value of the Python function is system-dependent.

os.wait()

Wait for completion of a child process, and return a tuple containing its pid and exit status indication: a 16-bit number, whose low byte is the signal number that killed the process, and whose high byte is the exit status (if the signal number is zero); the high bit of the low byte is set if a core file was produced.

在您的例子中，二进制返回值 768 是 00000011 00000000。高字节为3。