R needs a TMPDIR during running of the submission

For the syntax check the current workdirectory `/compile` can be used.
This is safe as it is not available during judging.

Normally there is no writable directory during judgements, to make R
work for submissions you need to set DOMJUDGE_CREATE_WRITABLE_TEMP_DIR to create a
writable temporary directory with extra security risks.

Author: vmcj

sql/files/defaultdata/r/run

@@ -27,6 +27,10 @@ if [ ! -r "$MAINSOURCE" ]; then
 fi
 
 # Check syntax
+#
+# Store intermediate files in the current dir (/compile) as its only
+# available during compilation step.
+export TMPDIR=`pwd`
 Rscript -e "parse('"$@"')"
 EXITCODE=$?
 [ "$EXITCODE" -ne 0 ] && exit $EXITCODE
@@ -45,10 +49,14 @@ fi
 # debugging.
 # export ONLINE_JUDGE=1 DOMJUDGE=1
 
+# Rscript needs a temporary directory which is a security risk.
+# To make the language work you'll need to set DOMJUDGE_CREATE_WRITABLE_TEMP_DIR=1
+# as environment variable when starting the judgedaemon:
+# DOMJUDGE_CREATE_WRITABLE_TEMP_DIR=1 bin/judgedaemon
+
 exec Rscript "$MAINSOURCE" "\$@"
 EOF
 
 chmod a+x "$DEST"
 
 exit 0
-