Command line size limitation

[A----]

There's a finite amount of characters that can be used on the command line. This limit varies across systems and all but if a user adds too many pages, this can cause the process to fail or output unexpected results.

wkhtmltopdf seems to handle this issue by providing the --read-args-from-stdin parameters, with the following documentation:

Reading arguments from stdin:
  If you need to convert a lot of pages in a batch, and you feel that
  wkhtmltopdf is a bit too slow to start up, then you should try
  --read-args-from-stdin,

  When --read-args-from-stdin each line of input sent to wkhtmltopdf on stdin
  will act as a separate invocation of wkhtmltopdf, with the arguments specified
  on the given line combined with the arguments given to wkhtmltopdf

  For example one could do the following:

  echo "http://qt-project.org/doc/qt-4.8/qapplication.html qapplication.pdf" >> cmds
  echo "cover google.com http://en.wikipedia.org/wiki/Qt_(software) qt.pdf" >> cmds
  wkhtmltopdf --read-args-from-stdin --book < cmds

See there: https://wkhtmltopdf.org/usage/wkhtmltopdf.txt

Also, I wonder if it would be possible to “demonize” the process by never closing the stdin of wkhtmltopdf, printing/flushing a line whenever a PDF is required.