使用 StringIO 作为 Popen 的标准输入

问题描述

我有以下我想用 Python 编写的 shell 脚本(当然 grep . 实际上是一个更复杂的命令):

I have the following shell script that I would like to write in Python (of course grep . is actually a much more complex command):

#!/bin/bash

(cat somefile 2>/dev/null || (echo 'somefile not found'; cat logfile)) 
| grep .

我试过这个(无论如何它都缺少与 cat logfile 等效的东西):

I tried this (which lacks an equivalent to cat logfile anyway):

#!/usr/bin/env python

import StringIO
import subprocess

try:
    myfile = open('somefile')
except:
    myfile = StringIO.StringIO('somefile not found')

subprocess.call(['grep', '.'], stdin = myfile)

但我得到错误 AttributeError: StringIO instance has no attribute 'fileno'.

我知道我应该使用 subprocess.communicate() 而不是 StringIO 将字符串发送到 grep 进程，但我不知道如何混合使用这两个字符串和文件.

I know I should use subprocess.communicate() instead of StringIO to send strings to the grep process, but I don't know how to mix both strings and files.

推荐答案

p = subprocess.Popen(['grep', '...'], stdin=subprocess.PIPE, 
                                      stdout=subprocess.PIPE)
output, output_err = p.communicate(myfile.read())

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