从二进制文件读取字符串 [英] Read string from binary file

问题描述

我想从文件中读取字节1,2和3.我知道它对应一个字符串(在这种情况下，它是Linux二进制标头的ELF)

I want to read bytes 1,2 and 3 from a file. I know it corresponds to a string (in this case it's ELF of a Linux binary header)

以下是我在网上可以找到的示例:

Following examples I could find on the net I came up with this:

with open('hello', 'rb') as f:
    f.seek(1)
    bytes = f.read(3)
    string = struct.unpack('s', bytes)
    print st

查看 struct 的官方文档，似乎通过了s作为参数应该允许我读取字符串.

Looking at the official documentation of struct it seems that passing s as argument should allow me to read a string.

我得到了错误:

st = struct.unpack('s', bytes)
struct.error: unpack requires a string argument of length 1

使用Python 2.7

Using Python 2.7

推荐答案

在您的特殊情况下，只需进行检查即可

In your special case, it is enough to just check

if bytes == 'ELF':

一步测试所有三个字节为三个字符E，L和F.

to test all three bytes in one step to be the three characters E, L and F.

但是，如果您要检查数值，则无需在此处解包任何内容.只需使用ord(bytes[i])(i分别为0、1、2)来获取三个字节的字节值即可.

But also if you want to check the numerical values, you do not need to unpack anything here. Just use ord(bytes[i]) (with i in 0, 1, 2) to get the byte values of the three bytes.

或者您可以使用

byte_values = struct.unpack('bbb', bytes)

获得三个字节的元组.如果字节具有如下可命名的语义，您也可以即时解开该元组:

to get a tuple of the three bytes. You can also unpack that tuple on the fly in case the bytes have nameable semantics like this:

width, height, depth = struct.unpack('bbb', bytes)

使用'BBB'代替'bbb'，以防您的字节值无符号.

Use 'BBB' instead of 'bbb' in case your byte values shall be unsigned.

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