问题描述
我需要这样做:
paste file1 file2 file3 > result
我的 python 脚本中有以下内容:
I have the following in my python script:
from subprocess import call
// other code here.
// Here is how I call the shell command
call ["paste", "file1", "file2", "file3", ">", "result"])
很遗憾，我收到了这个错误:
Unfortunately I get this error:
paste: >: 没有这样的文件或目录.
对此的任何帮助都会很棒！
Any help with this will be great!
推荐答案
有两种方法.
使用
shell=True:
call("paste file1 file2 file3 >result", shell=True)
重定向，>，是一个shell特性.因此，您只能在使用 shell 时访问它:shell=True.
Redirection, >, is a shell feature. Consequently, you can only access it when using a shell: shell=True.
保持shell=False，使用python进行重定向:
Keep shell=False and use python to perform the redirection:
with open('results', 'w') as f:
subprocess.call(["paste", "file1", "file2", "file3"], stdout=f)
第二个通常是首选，因为它避免了 shell 的变幻莫测.
The second is normally preferred as it avoids the vagaries of the shell.
不使用 shell 时，> 只是命令行上的另一个字符.因此，请考虑错误消息:
When the shell is not used, > is just another character on the command line. Thus, consider the error message:
paste: >: No such file or directory.
这表明 paste 已收到 > 作为参数，并试图打开该名称的文件.不存在这样的文件.因此消息.
This indicates that paste had received > as an argument and was trying to open a file by that name. No such file exists. Therefore the message.
作为 shell 命令行，可以使用该名称创建文件:
As the shell command line, one can create a file by that name:
touch '>'
如果存在这样的文件，当 subprocess 使用 shell=False 调用 paste 时，会使用该文件作为输入.
If such a file had existed, paste, when called by subprocess with shell=False, would have used that file for input.
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