如何读取包含 NUL 字符的文本文件？

Question

I have a file that contains NUL characters.

This file is generated by another program I have no control over, but I have to read it in order to get some crucial information.

Unfortunately, readChar() truncates the output with this warning:

 In readChar("output.txt", 1e+05): truncating string with embedded nuls

Is there a way around this problem?

Answer 1

By convention, a text file cannot contain non-printable characters (including NUL). If a file contains such characters, it isn't a text file — it's a binary file.

R strictly ¹ adheres to this convention, and completely disallows NUL characters. You really need to read and treat the data as binary data. This means using readBin and the raw data type:

n = file.size(filename)
buffer = readBin(filename, 'raw', n = n)
# Unfortunately the above has a race condition, so check that the size hasn’t changed!
stopifnot(n == file.size(filename))

Now we can fix the buffer by removing embedded zero bytes. This assumes UTF- x or ASCII encoding! Other encodings might have embedded zero bytes that need to be interpreted!

buffer = buffer[buffer != 0L]
text = rawToChar(buffer)

---

¹ Maybe too strictly …