Made the document conversion multithreaded, to speed up the script (50% reduction in time)

build.sh

@@ -144,7 +144,9 @@ replace_vars() {
 
 md_to_html() {
 #	Convert .md files from 'source' and place them into the correct locations into 'output'
-
+#	Since the conversion is the slowest part of the script, I run each conversion process
+#	in a separate thread (first loop). Then I wait for all of them to finish, and add the 
+#	header and footers and replace the variables in each converted document (second loop).
 	local files=$(find "$BASE_PATH/source" -name "*.md")
 
 	for file in $files; do
@@ -153,9 +155,6 @@ md_to_html() {
 
 		read_metadata "$file" # Sets the 'metadata' variable
 
-		convert_to_array "$metadata" #Sets the 'meta_array' array
-		add_date_to_array "$file" #Uses 'meta_array' array
-
 #		Copy file to temp dir and strip metadata
 		cp "$file" "$BASE_PATH/temp/"
 		let num_lines=$(echo "$metadata" | wc -l)+1
@@ -166,10 +165,32 @@ md_to_html() {
 		path_for_output="${BASE_PATH}/output/${path_for_output}"
 		path_for_output="$(dirname $path_for_output)/$(basename $path_for_output .md).html"
 
-#		Convert the file (using the given filters), and place the output in the correct location
-		pandoc --lua-filter "$BASE_PATH"/pandoc_filters/* -f markdown --wrap=preserve "$BASE_PATH/temp/$(basename "$file")" > "${path_for_output}"
+#		Convert the file (using the given filters), and place the output in the correct location.
+#		The process is forked, so that all documents can be converted concurrently.
+		(pandoc --lua-filter "$BASE_PATH"/pandoc_filters/* -f markdown --wrap=preserve "$BASE_PATH/temp/$(basename "$file")" > "${path_for_output}") &
+
+		unset metadata
+	done
+
+#	Wait for all documents to finish converting, then remove all temporary files.
+	wait
 	rm "$BASE_PATH"/temp/*
 	
+	for file in $files; do
+#		This function was already called above in the previous loop.
+#		However, I need to call it again, since I need the metadata 
+#		again for each file to create the 'meta_array' variable.
+		read_metadata "$file" # Sets the 'metadata' variable
+
+		convert_to_array "$metadata" #Sets the 'meta_array' array
+		add_date_to_array "$file" #Uses 'meta_array' array
+
+#		Construct path for output file. This is the same path that the converted
+#		document is written to, in the loop above.
+		local path_for_output=$(realpath --relative-to="${BASE_PATH}/source" "$file")
+		path_for_output="${BASE_PATH}/output/${path_for_output}"
+		path_for_output="$(dirname $path_for_output)/$(basename $path_for_output .md).html"
+
 		add_header_and_footer "$path_for_output" # Uses 'meta_array' array
 		replace_vars "$path_for_output" #Uses 'meta_array' array