How to escape a space in a path on msys2?

I want to invoke C:\Program Files (x86)\Leela\Leela0100.exe and pass it a filename:

#!/bin/bash -x

BASE="c:/Users/supreme"
DROPBOX="$BASE/Dropbox"

DOWNLOADS="$BASE/Downloads"

cd $DOWNLOADS
SGF=`ls -th *.sgf | head -1`

GAMES="$DROPBOX/Baduk/Games"

mv $SGF $GAMES

LEELA='c://Program Files (x86)//Leela//Leela0100.exe'

cd $GAMES
$LEELA $SGF

However, invoking my script via bash -x toleela.sh under MSYS2 yields the error:

c:\Users\supreme\Dropbox\Programming>bash -x toleela.sh 
bash -x toleela.sh 
+ BASE=c:/Users/supreme
+ DROPBOX=c:/Users/supreme/Dropbox
+ DOWNLOADS=c:/Users/supreme/Downloads
+ cd c:/Users/supreme/Downloads
++ ls -th '9001447-269-Winggo-princepawn (1).sgf' 9429961-080-princepawn-RyanBLee.sgf
++ head -1
+ SGF=9429961-080-princepawn-RyanBLee.sgf
+ GAMES=c:/Users/supreme/Dropbox/Baduk/Games
+ mv 9429961-080-princepawn-RyanBLee.sgf c:/Users/supreme/Dropbox/Baduk/Games
+ LEELA='c://Program Files (x86)//Leela//Leela0100.exe'
+ cd c:/Users/supreme/Dropbox/Baduk/Games
+ c://Program Files '(x86)//Leela//Leela0100.exe' 9429961-080-princepawn-RyanBLee.sgf
toleela.sh: line 18: c://Program: No such file or directory

Solution

As was already pointed out to you on IRC, you are missing quotes around the variable expansions on the last line of your script (also on other lines).

"$LEELA" "$SGF"

The double forward slashes (//) in your executable path are not right. Use single forward slash (/) ~~or a double backslash (\\)~~ instead. EDIT: Backslashes are more complicated, so stick to forward ones.