Make sh scrips POSIX compliant

Using shellcheck, I went through all of them to make them standards
compliant. I also tested as many as I could.

1 files changed, 3 insertions, 6 deletions

diff --git a/dmenu_books b/dmenu_books
index 3b6f1fe..a579476 100755
--- a/dmenu_books
+++ b/dmenu_books
@@ -5,15 +5,12 @@ printhelp () {
 }
 
 while getopts "hd:" o; do case "${o}" in
-  d) ARGS="$ARGS$OPTARG " ;;
+  d) ARG="$OPTARG" ;;
   *) printhelp ;;
 esac done
 
-DMENU="dmenu"
-DEFARGS="-l 15 -p"
-
-BOOK=`ls ~/Documents/shared | $DMENU $DEFARGS \"books\" $ARGS`
+BOOK=$(find ~/Documents/shared | dmenu -l 15 -p \"books\" ${ARG:+"$ARG"})
 
 [ -z "$BOOK" ] && exit 1
 
-zathura "~/Documents/shared/$BOOK"
+zathura "$HOME/Documents/shared/$BOOK"