rotpdf

#!/usr/bin/env bash

die() { printf %s "${@+$@$'\n'}" 1>&2 ; exit 1 ; }
see() ( { set -x; } 2>/dev/null ; "$@" ) ;

command -v qpdf > /dev/null || die "qpdf needs to be installed"

do1file() (
   fnm="$1"
   if [[ ! -f "$fnm" ]]; then
      echo "$fnm does not name a file"
      return
   fi
   # break down $fnm:
   fpath=""
   if [[ $fnm == */* ]]; then
      fpath="${fnm%/*}/"
      cd "$fpath" || die "cd to $fpath failed"
   fi                                   # ; echo "fpath=$fpath'"
   # note that because we cd above, remaining filenames used are sanspath
   sanspath="${fnm##*/}"                # ; echo "sanspath=$sanspath'"    # https://stackoverflow.com/a/965069
   ext="${sanspath##*.}"                # ; echo "ext=$ext'"
   sansext="${sanspath%.*}"             # ; echo "sansext=$sansext'"
   # logical parameters:
   bakfnm="${sansext}_orig.$ext"          ; echo "bakfnm  $bakfnm"
   destfnm="$sanspath"                    ; echo "destfnm $destfnm'"
   mv -n "$destfnm" "$bakfnm" || die "backup-create move failed"
   dorot "$bakfnm" "$destfnm"
   )

# EX: rotate *select* pages in pdf
#     qpdf src.pdf --rotate=+90:19-21,24-30,43-49 -- out.pdf
# EX: merge/cat whole pdf files into one
#     qpdf --empty --pages *.pdf -- out.pdf
# EX: extract page range from in.pdf into out.pdf (note the '.')  https://askubuntu.com/a/672001
#     qpdf in.pdf --pages . 1-16 -- out.pdf

dorot() ( qpdf --rotate="$rotdeg" "$1" "$2" )

help() { die "need rotmode file [file...] where rotmode is one of cw ccw 180" ; }

rotmode="$1" ; shift || help
case $rotmode in
  cw)  rotdeg=+90 ;;
  ccw) rotdeg=-90 ;;
  180) rotdeg=180 ;;
  \?)  help       ;;
esac
[[ "$rotdeg" ]] || help
[[ "$1" ]] || echo "missing name of file(s) to rotate"

for fnm in "$@"; do
   do1file "$fnm"
done