allow users to override the FLAGS_EXPR_CMD variable
diff --git a/source/1.0/src/shflags b/source/1.0/src/shflags
index 9a61d7a..4177ac9 100644
--- a/source/1.0/src/shflags
+++ b/source/1.0/src/shflags
@@ -87,16 +87,16 @@
[ -n "${FLAGS_VERSION:-}" ] && return 0
FLAGS_VERSION='1.0.4pre'
-FLAGS_UNAME_S=`uname -s`
-
-# Different OSes need different commands.
-case "${FLAGS_UNAME_S}" in
- BSD) FLAGS_EXPR_CMD='gexpr' ;;
- *) FLAGS_EXPR_CMD='expr' ;;
+# Set some reasonable defaults.
+__FLAGS_UNAME_S=`uname -s`
+case "${__FLAGS_UNAME_S}" in
+ BSD) __FLAGS_EXPR_CMD='gexpr' ;;
+ *) __FLAGS_EXPR_CMD='expr' ;;
esac
-# A user can set the path to a different getopt command by overriding this
-# variable in their script.
+# A user can set the path to different commands by overriding these variables in
+# their script.
+FLAGS_EXPR_CMD=${FLAGS_EXPR_CMD:-${__FLAGS_EXPR_CMD}}
FLAGS_GETOPT_CMD=${FLAGS_GETOPT_CMD:-getopt}
# return values that scripts can use