In /usr/bin/gslp line 6:
gs="`dirname \"$0\"`/$GS_EXECUTABLE"
    ^--------------^ SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean: 
gs="$(dirname \"$0\")/$GS_EXECUTABLE"


In /usr/bin/gslp line 12:
exec "$GS_EXECUTABLE" -q -sDEVICE=epson -r180 -P- -dSAFER -dNOPAUSE -sPROGNAME=$0 -- gslp.ps --heading-center "`date`" "$@"
                                                                               ^-- SC2086: Double quote to prevent globbing and word splitting.
                                                                                                               ^----^ SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean: 
exec "$GS_EXECUTABLE" -q -sDEVICE=epson -r180 -P- -dSAFER -dNOPAUSE -sPROGNAME="$0" -- gslp.ps --heading-center "$(date)" "$@"

For more information:
  https://www.shellcheck.net/wiki/SC2086 -- Double quote to prevent globbing ...
  https://www.shellcheck.net/wiki/SC2006 -- Use $(...) notation instead of le...