sha256sum --text generating blank spaces and hyphens?

[Albretch Mueller <lbrtchx@gmail.com>]

 This is not a debian question per se (more like a Linux bash one),
but I wasn't able to find an answer on the Internet.

 Here is first the problem I am having before you start reading a
conspiracy theory into it ;-)

 I need to somehow map URL on the web to a local file, but you can't
do that for two main reasons:

 1) URLs are free text
 2) which people take to their heart's content.

 Take for example:

 https://dokumen.pub/qdownload/nietzsche-und-der-deutsche-geist-band-4-ausbreitung-und-wirkung-des-nietzscheschen-werkes-im-deutschen-sprachraum-bis-zum-ende-des-zweiten-weltkrieges-ein-schrifttumsverzeichnis-der-jahre-1867-1945-ergnzungen-berichtigungen-und-gesamtverzeichnisse-zu-den-bnden-i-iii-9783110202861-9783110189865-3110189860.html

 that file and the pdf you would download I need to map to a local
directory looking like: ... /pub/dokumen/qdownload/ ...

 but the file name (excluding the extension) is 306 characters long,
which Windows NTFS would not swallow. There may be also funky rules
regarding character sets and where in a string certain chars may be
used; so, as a way to work around those kinds of problems I:

 a) encode the string name as base64
 b) calculate the sha256sum of §a
 c) use §b as file name (of course, leaving the original extension as it is)
 d) include a "§b_file_name.txt" plain text file decriptor which only
content is the actual prehash name of that file.


 https://dokumen.pub/qdownload/nietzsche-und-der-deutsche-geist-band-4-ausbreitung-und-wirkung-des-nietzscheschen-werkes-im-deutschen-sprachraum-bis-zum-ende-des-zweiten-weltkrieges-ein-schrifttumsverzeichnis-der-jahre-1867-1945-ergnzungen-berichtigungen-und-gesamtverzeichnisse-zu-den-bnden-i-iii-9783110202861-9783110189865-3110189860.html
 _TXT="nietzsche-und-der-deutsche-geist-band-4-ausbreitung-und-wirkung-des-nietzscheschen-werkes-im-deutschen-sprachraum-bis-zum-ende-des-zweiten-weltkrieges-ein-schrifttumsverzeichnis-der-jahre-1867-1945-ergnzungen-berichtigungen-und-gesamtverzeichnisse-zu-den-bnden-i-iii-9783110202861-9783110189865-3110189860"
 _B64TXTENC=$(printf '%s' "${_TXT}" | base64 )
 echo "// __ \$_B64TXTENC: |${_B64TXTENC}|"
 _B64TXTDEC=$(printf '%s' "${_B64TXTENC}" | base64 --decode)
 echo "// __ \$_B64TXTDEC: |${_B64TXTDEC}|"
 if [[ "${_TXT}" == "${_B64TXTDEC}" ]]; then
  echo "// __ [[ \${_TXT} == \${_B64TXTDEC} ]]: |${_TXT}|"
  _SHA256=$(printf '%s' "${_TXT}" | sha256sum --text )
  echo "// __ \$_SHA256: |${_SHA256}|"
 fi

// __ $_SHA256:
|7d5895cb24ab49692a8ad495e036074fec8e61b22040544f02a9b69c926dbdeb  -|

 I am trying to avoid funky characters and sha256sum --text still
generates them!?!

 I work like this because I need replicate the original URL as a local
path in a way that would be compatible any file system.

 Do you know of a better way to deal with such issues?

 lbrtchx