在 subprocess.call 中使用大于运算符

2022-01-18 00:00:00 python subprocess call

问题描述

我想做的很简单.我想使用 python 的 subprocess 模块调用以下命令.

What I am trying to do is pretty simple. I want to call the following command using python's subprocess module.

cat /path/to/file_A > file_B

该命令简单地工作并将file_A的内容复制到当前工作目录中的file_B.但是，当我尝试在脚本中使用 subprocess 模块调用此命令时，它会出错.以下是我正在做的事情:

The command simply works and copies the contents of file_A to file_B in current working directory. However when I try to call this command using the subprocess module in a script it errors out. Following is what I am doing:

import subprocess

subprocess.call(["cat", "/path/to/file_A", ">", "file_B"])

我收到以下错误:

cat: /path/to/file_A: No such file or directory
cat: >: No such file or directory
cat: file_B: No such file or directory

我做错了什么?如何在子进程模块 call 命令中使用大于运算符?

what am I doing wrong ? How can I use the greater than operator with subprocess modules call command ?

解决方案

> 输出重定向是 shell 功能，但是 subprocess.call() 带有 args 列表和 shell=False(默认)不使用 shell.

> output redirection is a shell feature, but subprocess.call() with an args list and shell=False (the default) does not use a shell.

您必须在此处使用 shell=True:

subprocess.call("cat /path/to/file_A > file_B", shell=True)

或者更好的是，使用 subprocess 将命令的输出重定向到文件:

or better still, use subprocess to redirect the output of a command to a file:

with open('file_B', 'w') as outfile:
    subprocess.call(["cat", "/path/to/file_A"], stdout=outfile)

如果您只是复制文件，请使用 shutil.copyfile() 函数 让 Python 复制文件:

If you are simply copying a file, use the shutil.copyfile() function to have Python copy the file across:

import shutil

shutil.copyfile('/path/to/file_A', 'file_B')

相关文章