带有shell = True的Python子进程不允许进行进程替换吗? [英] Process substitution not allowed by Python's subprocess with shell=True?

问题描述

这是一个过程替换的玩具示例，在Bash中效果很好:

Here is a toy example of process substitution that works fine in Bash:

$ wc -l <(pwd)
1 /proc/self/fd/11

那么，当从shell的shell = True的Python子进程中调用该命令时，为什么同一命令会给出语法错误?

So why does the same command give a syntax error when invoked from Python's subprocess with shell=True?

>>> subprocess.check_call('wc -l <(pwd)', shell=True)
/bin/sh: 1: Syntax error: "(" unexpected
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/path/to/my/python/lib/python3.5/subprocess.py", line 581, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command 'wc -l <(pwd)' returned non-zero exit status 2

推荐答案

/bin/sh:1:语法错误:("意外

/bin/sh: 1: Syntax error: "(" unexpected

您有 bashism .根据POSIX无效，这是/bin/sh 实现的.

You have a bashism. It is not valid according to POSIX, which is what /bin/sh implements.

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