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'''CAVEAT'''. This recipe was cooked in Linux and uses the file <code>/dev/urandom</code> which will be present in all Unix-like systems as far as the author knows. So, Linux, Mac, BSD are all fine.

Sometimes your file contains stuff which is not intended to be interpreted as a sequence of characters. This can be the case, for example, if you are reading/writing some compressed data, some audio file, a big matrix, a picture etc.

== Reading from a binary file ==
'''Problem'''. I want to have a quite good random number and I know than most Unix systems provide a file <code>/dev/urandom</code> where I can read as many as I want. Please see your operating system documentation of the file to know how it works. This is a classic example of a binary stream, when I read from <code>/dev/urandom</code> I am supposed to read byte per byte, e.g. it would make not much sense to try to read a line. Also, this example is nice because you are not supposed to read in all the file, since this file has no end! You must read only a certain amount of it.

'''Solution'''. Follow the sequence of commands below to see how you can read from <code>/dev/urandom</code> as a binary stream.
"Make a ReadStream from a file"
rs _ '/dev/urandom' asFileEntry readStream.
rs class. "=> StandardFileStream "

" generally you may want to read a binary stream as a sequence of bytes."
rs useBytes .

" get the fisrt byte"
rs next. "=> 7 "

"get the following 10 bytes"
tmp _ rs next: 10. "=> #[192 101 93 30 46 183 55 186 231 66] "
tmp class. "=> ByteArray "

" get 'tmp' in hex format, spaces added for readability by hand "
tmp hex. " 'EF F6 F0 1A 78 14 C0 02 73 1C' "

" get 'tmp' as base64, will make it shorter "
tmp base64Encoded . "=> '15vGaEu2IU1NAQ==' "

" let's see what comes back if we read in binary mode"
tmp2 _ rs next. "=> 238 "
tmp2 class. "=> SmallInteger "

" we may want to read the binary stream as characters "
rs useCharacters .
rs next: 10. "=> ')Orý»¯ÊÂ³' "

" when you finished remember to close the stream. "
rs close.

== TODO: Writing a binary file ==
To remember here is that <code>writeStream</code> asks confirmation if the file already exists, to have no question asked use <code>forceWriteStream</code>.
----Dr. Nicola Mingotti last updated this on 3-Sep-2021. Examples where run in Cuis-5.0-4815.image.

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