为什么Python Popen会忽略字符'^' - 如何在Popen Windows中转义'^'字符? [英] Why character '^' is ignored byt Python Popen - how to escape '^' character in Popen Windows?
问题描述
我准备了一些代码来执行这样的命令行:
c:\ cygwin \ bin\convertc :\root\dropbox\www\tiff\photos\architecture\calendar-BWL-projekt\bwl01.tif -thumbnail 352x352 ^ -format JPG型滤波器Catrom -unsharp为0x1 C:\ root\dropbox\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
这可以从命令行运行(与上面相同的命令),但352x352 ^是352x352 ^不是352x352:
c:\ cygwin \ bin\convertc:\root \ dropbox \\\\tiff\photos \architecture \ calendar-bwl-projekt \ bwl01.tif -thumbnail 352x352 ^ -format JPG型滤波器Catrom -unsharp为0x1 C:\root\dropbox\www\tiff\thumbnails\architecture\calendar-BWL-projekt\thumbnail\bwl01.jpg
如果从py运行此代码thon - 字符'^'被忽略,调整大小的图像的大小为'%sx%s'传递而不是%sx%s ^ - 为什么Python剪切'^'字符以及如何避免它?:
def resize_image_to_jpg(input_file,output_file,size):
resize_command ='c:\\cygwin \ \\\\\转换%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'^'字符以及如何避免它?
Python不会削减 ^
字符。 Popen()
将字符串( resize_command
)传递给 CreateProcess()
Windows API调用原样。
很容易测试:
#!/ usr / bin / env python
import sys
import subprocess
subprocess.check_call([sys.executable,' - c','import sys; print(sys.argv)'] +
['^','< - 看,它还在这里'])
后一个命令使用<$ href =http://msdn.microsoft.com/之后的 subprocess.list2cmdline()
en-us / library / a1y7w461.aspxrel =nofollow>解析C命令行参数规则将列表转换为命令字符串 - 它对 ^ <没有影响/ code>。
^
对于 CreateProcess()
并不特殊。 ^
如果您使用 shell = True
(当 cmd.exe $ c时)是特殊的$ c>正在运行)
。
当且仅当生成的命令行将由cmd解释时,为每个shell元字符添加前缀(或每个字符)带有 ^
字符。它包括 ^
本身。
I prepared some code to execute such command line:
c:\cygwin\bin\convert "c:\root\dropbox\www\tiff\photos\architecture\calendar-bwl-projekt\bwl01.tif" -thumbnail 352x352^ -format jpg -filter Catrom -unsharp 0x1 "c:\root\dropbox\www\tiff\thumbnails\architecture\calendar-bwl-projekt\thumbnail\bwl01.jpg"
This works fine from command line (same command as above) but 352x352^ is 352x352^ not 352x352:
c:\cygwin\bin\convert "c:\root\dropbox\www\tiff\photos\architecture\calendar-bwl-projekt\bwl01.tif" -thumbnail 352x352^ -format jpg -filter Catrom -unsharp 0x1 "c:\root\dropbox\www\tiff\thumbnails\architecture\calendar-bwl-projekt\thumbnail\bwl01.jpg"
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
Why Python cuts '^' character and how to avoid it?
Python does not cut ^
character. Popen()
passes the string (resize_command
) to CreateProcess()
Windows API call as is.
It is easy to test:
#!/usr/bin/env python
import sys
import subprocess
subprocess.check_call([sys.executable, '-c', 'import sys; print(sys.argv)'] +
['^', '<-- see, it is still here'])
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 ^
.
^
is not special for CreateProcess()
. ^
is special if you use shell=True
(when cmd.exe
is run).
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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