Don't shell out to kpsewhich for undefined variables.

diff --git a/makefile b/makefile
index d9bd9d5f3a19f7ad0cc427d2ce7adaa0b0c86f61..a0b130edc7c686774b989b9eb5695d778d3332c2 100644 (file)
--- a/makefile
+++ b/makefile
@@ -25,7 +25,13 @@ MJOTEX += mjo-theorem-star.tex mjo-topology.tex
 # Use kpsewhich (from the kpathsea suite) to find the absolute paths
 # of the bibtex/mjotex files listed in in $(BIBS)/$(MJOTEX). The SRCS
 # variable should contain all (Bib)TeX source files for the document.
-SRCS = $(PN).tex $(shell kpsewhich $(BIBS)) $(shell kpsewhich $(MJOTEX))
+SRCS = $(PN).tex
+ifdef BIBS
+SRCS += $(shell kpsewhich $(BIBS))
+endif
+ifdef MJOTEX
+SRCS += $(shell kpsewhich $(MJOTEX))
+endif
 
 
 # The first target is the default, so put the PDF document first.