script.sh

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#######################################################################
#      set up paths, the paths move around on repl                    #
#######################################################################
replrootpath=$PWD
cdate=$(date +%Y%m%dT%H%M%s)
export DISPLAY=:0.0
backuptargetname=$target_file$cdate
backupsourcename=$source_file$cdate
examplebasepath=$replrootpath/freeglut-3.2.1/progs/demos/

# name your files here - this is your own thing to edit/complile in C++ 
source_file=$replrootpath/'triangle.cpp'
target_file=$replrootpath/'triangle'


# check if freeglut3-dev is installed on host
# install it if one of the library files is missing
# see output of >ldd triangle< from shell for more info
if [ ! -f /home/runner/.apt/usr/lib/x86_64-linux-gnu/libglut.so.3 ]
then
  printf '\n%s\n' "library not installed, installing freeglut3-dev"
  install-pkg freeglut3-dev
fi




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##################################################################################
##     performs versioning, checks mtime on file to see                         ##
##     if cpp src file is modified newer than compiled binary                   ##
##     if so then move it to backup dir and remake with g++                     ##
##################################################################################
printf '\n%s\n' "Checking if source mtime is newer than main binary"
if [ "$source_file" -nt "$target_file" ]
then
    printf '%s\n\n' "$source_file is newer than $target_file , moving old to $newtargetname and compiling"
    mv $target_file backup/$backuptargetname
    cp $source_file backup/$backupsourcename
    g++ $source_file -lglut -lGL -lGLU -o $target_file
    chmod 744 ./$target_file
fi




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#################################################################################
#                 if we made it this far, start your program                    #
#################################################################################
printf '\n%s\n' "starting binary"
$target_file
echo "done"