为什么字符'^'被Python Popen忽略 - 如何在Popen Windows中转义'^'字符?

2022-01-18 00:00:00 python python-2.7 windows subprocess imagemagick

问题描述

我准备了一些代码来执行这样的命令行:

I prepared some code to execute such command line:

c:cygwininconvert "c:ootdropboxwww	iffphotosarchitecturecalendar-bwl-projektwl01.tif" -thumbnail 352x352^ -format jpg -filter Catrom -unsharp 0x1 "c:ootdropboxwww	iff	humbnailsarchitecturecalendar-bwl-projekt	humbnailwl01.jpg"

这在命令行中可以正常工作(与上面的命令相同)，但 352x352^ 是 352x352^ 而不是 352x352:

This works fine from command line (same command as above) but 352x352^ is 352x352^ not 352x352:

c:cygwininconvert "c:ootdropboxwww	iffphotosarchitecturecalendar-bwl-projektwl01.tif" -thumbnail 352x352^ -format jpg -filter Catrom -unsharp 0x1 "c:ootdropboxwww	iff	humbnailsarchitecturecalendar-bwl-projekt	humbnailwl01.jpg"

如果从 python 运行此代码 - 字符 '^' 被忽略并且调整大小的图像的大小为 '%sx%s' 传递而不是 %sx%s^ - 为什么 Python 会剪切 '^' 字符以及如何避免它?:

If run this code from python - character '^' is ignored and resized image has size as '%sx%s' is passed not %sx%s^ - Why Python cuts '^' character and how to avoid it?:

def resize_image_to_jpg(input_file, output_file, size):
  resize_command = 'c:\cygwin\bin\convert "%s" -thumbnail %sx%s^ -format jpg -filter Catrom -unsharp 0x1 "%s"' 
                   % (input_file, size, size, output_file)
  print resize_command
  resize = subprocess.Popen(resize_command)
  resize.wait()

解决方案

为什么 Python 会削减 '^' 字符以及如何避免?

Why Python cuts '^' character and how to avoid it?

Python 不会剪切 ^ 字符.Popen() 将字符串 (resize_command) 按原样传递给 CreateProcess() Windows API 调用.

Python does not cut ^ character. Popen() passes the string (resize_command) to CreateProcess() Windows API call as is.

很容易测试:

#!/usr/bin/env python
import sys
import subprocess

subprocess.check_call([sys.executable, '-c', 'import sys; print(sys.argv)'] +
                      ['^', '<-- see, it is still here'])

后一个命令使用 subprocess.list2cmdline()">Parsing C Command-Line Arguments 规则将列表转换为命令字符串 -- 它对 ^ 没有影响.

The latter command uses subprocess.list2cmdline() that follows Parsing C Command-Line Arguments rules to convert the list into the command string -- it has not effect on ^.

^ 对于 CreateProcess 来说并不特殊().^ 如果你使用 shell=True 是特殊的(当 cmd.exe 运行时).

^ is not special for CreateProcess(). ^ is special if you use shell=True (when cmd.exe is run).

当且仅当生成的命令行将由 cmd 解释，在每个 shell 元字符(或每个字符)前加上 ^ 字符.它包括 ^ 本身.

if and only if the command line produced will be interpreted by cmd, prefix each shell metacharacter (or each character) with a ^ character. It includes ^ itself.

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