Hexadecimal file is loading with 2 back slashes before each byte instead of one

Question

I have a hex file in this format: \xda\xd8\xb8\x7d

When I load the file with Python, it loads with two back slashes instead of one.

with open('shellcode.txt', 'r') as file: shellcode = file.read().replace('\n', '')

Like this: \\xda\\xd8\\xb8\\x7d

I've tried using hex.replace("\\", "\"), but I'm getting an error

EOL while scanning string literal

What is the proper way to replace \\ with \?

Those are backslashes, not forward slashes. The first one escapes the second one. There isn't a problem. Try printing the string — joel goldstick
– joel goldstick, Commented Sep 17, 2016 at 19:17
Use raw strings hex.replace(r"\\", r"\") You escaped the final double-quote, hence the error. However I'm dubious if the characters really look like this as a string, or this is just a string representation of the data. — cdarke
– cdarke, Commented Sep 17, 2016 at 19:17
How did you display the data? Please show your code. If repr() is used (which interactive python uses) the the extra \ will be seen, but if str() is used (which print uses) then it will not be added. — cdarke
– cdarke, Commented Sep 17, 2016 at 19:23
@cdarke this hex is not used in the Python program. I'm doing security work, and this hex is sent to another program to be executed as raw hex. — 123
– 123, Commented Sep 17, 2016 at 19:26
So how do you know there are two backslashes? How is it being displayed? Did you try raw strings? — cdarke
– cdarke, Commented Sep 17, 2016 at 19:27

joel goldstick · Accepted Answer · 2016-09-17 19:18:50Z

Here is an example

>>> h = "\\x123" >>> h '\\x123' >>> print h \x123 >>>

The two backslashes are needed because \ is an escape character, and so it needs to be escaped. When you print h, it shows what you want

zvone · Accepted Answer · 2016-09-17 19:40:13Z

Backshlash (\) is an escape character. It is used for changing the meaning of the character(s) following it.

For example, if you want to create a string which contains a quote, you have to escape it:

s = "abc\"def" print s # prints: abc"def

If there was no backslash, the first quote would be interpreted as the end of the string.

Now, if you really wanted that backslash in the string, you would have to escape the bacsklash using another backslash:

s = "abc\\def" print s # prints: abc\def

However, if you look at the representation of the string, it will be shown with the escape characters:

print repr(s) # prints: 'abc\\def'

Therefore, this line should include escapes for each backslash:

hex.replace("\\", "\") # wrong hex.replace("\\\\", "\\") # correct

But that is not the solution to the problem!

There is no way that file.read().replace('\n', '') introduced additional backslashes. What probably happened is that OP printed the representation of the string with backslashes (\) which ended up printing escaped backslashes (\\).

Zach Gates · Accepted Answer · 2016-09-17 20:27:21Z

You can make a bytes object with a utf-8 encoding, and then decode as unicode-escape.

>>> x = "\\x61\\x62\\x63" >>> y = bytes(x, "utf-8").decode("unicode-escape") >>> print(x) \x61\x62\x63 >>> print(y) abc

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