尝试将命令行输出保存到文件时出错 [英] Errors when trying to save command line output to a file

问题描述

我正在运行一个python工具，并尝试将其输出保存到一个文件。如果我不保存输出到一个文件，该工具运行完美。但是当我尝试将输出保存到文件时，它会抛出以下错误并中断程序：

I was running a python tool and trying to save its output to a file. If I don't save the output to a file, the tool runs perfectly fine. But when I try to save the output to the file, it throws following error and interrupt the program:

  File "./androdiff.py", line 118, in <module>
main(options, arguments)
  File "./androdiff.py", line 94, in main
ddm.show()
  File "./elsim/elsim/elsim_dalvik.py", line 772, in show
self.eld.show()
  File "./elsim/elsim/elsim.py", line 435, in show
i.show()
  File "./elsim/elsim/elsim_dalvik.py", line 688, in show
  print hex(self.bb.bb.start + self.offset), self.pos_instruction, self.ins.get_name(), self.ins.show_buff( self.bb.bb.start + self.offset )
  UnicodeEncodeError: 'ascii' codec can't encode character u'\u0111' in position 35: ordinal not in range(128)

我尝试过 command | less ， command>输出和命令|

I've tried command |less , command > output and command | tee output, all of them will throw such error.

请帮助解决这个问题。

谢谢！

推荐答案

您需要在打印之前指定字符串的编码：

You will want to specify the encoding of your string before you print it:

print unicode(hex(self.bb.bb.start + self.offset)).encode('utf-8')
print unicode(self.pos_instruction, self.ins.get_name()).encode('utf-8')
print unicode(self.ins.show_buff( self.bb.bb.start + self.offset )).encode('utf-8')

这是因为python会自动

The reason this works is because python automatically encodes your string correctly (in your case utf-8) when printing to the terminal (it detects that the terminal uses utf-8).

当您将输出重定向到终端时，字符串正确地输出到终端（在您的情况下是utf-8）文件改为，Python没有关于应该使用什么编码的信息，它默认为ascii（这导致您的错误）。

When you are redirecting your output to a file instead, Python has no information about what encoding it should use and it defaults to ascii instead (which is causing your error).

作为一般的经验法则确保您始终在打印之前对字符串进行编码，以使打印在所有环境中都可正常工作。

As a general rule of thumb, make sure you always encode your string before printing to make print work in all environments.

最好的方法是定义您自己的打印方法：

The best method may be to define your own print method for this:

def myprint(unicodestr): 
    print unicodestr.encode('utf-8')

如果您想避免上述操作并使用utf-8编码进行打印可以做

If you want to avoid the above and make printing with utf-8 encoding the default you can do

import sys
import codecs
sys.stdout=codecs.getwriter('utf-8')(sys.stdout)

注意这种方法！一些第三方库可能依赖于ascii和break的默认编码。注意，这整个混乱已经解决在Python 3（默认为UTF-8编码）

Beware of this approach! Some third-party libraries may depend on the default encoding being ascii and break. Note that this whole mess has been resolved in Python 3 (which defaults to UTF-8 encoding)

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