Add function to check for installed program

Notifies if program is missing.

.local/bin/compile

@@ -15,8 +15,11 @@ base="${file%.*}"
 cd "$dir" || exit
 
 textype() {
-  command="pdflatex"
-  (sed 5q "$file" | grep -i -q 'xelatex') && command="xelatex"
+  if (sed 5q "$file" | grep -i -q 'xelatex') && ifinstalled xelatex; then
+    command="xelatex"
+  elif ifinstalled pdflatex; then
+    command="pdflatex"
+  fi
   $command --output-directory="$dir" "$base" &&
     grep -i addbibresource "$file" >/dev/null &&
     biber --input-directory "$dir" "$base" &&
@@ -24,11 +27,15 @@ textype() {
     $command --output-directory="$dir" "$base"
 }
 
+sendtoRmd() {
+  ifinstalled R && echo "require(rmarkdown); render('$1')" | R -q --vanilla
+}
+
 case "$file" in
 *\.ms) refer -PS -e "$file" | groff -me -ms -kept -T pdf >"$base".pdf ;;
 *\.mom) refer -PS -e "$file" | groff -mom -kept -T pdf >"$base".pdf ;;
 *\.[0-9]) refer -PS -e "$file" | groff -mandoc -T pdf >"$base".pdf ;;
-*\.[Rr]md | *\.md | *\.mkd | *\.markdown) echo "require(rmarkdown); render('$file')" | R -q --vanilla ;;
+*\.[Rr]md | *\.md | *\.mkd | *\.markdown) sendtoRmd "$file" ;;
 *\.tex) textype "$file" ;;
 *config.h) sudo make install ;;
 *\.c) cc "$file" -o "$base" && "$base" ;;

.local/bin/ifinstalled

@@ -0,0 +1,4 @@
+#!/usr/bin/env sh
+# If $1 command is not available, error code and notify.
+
+command -v "$1" >/dev/null || { notify-send "📦 $1" "must be installed for this function." && exit 1 ;}