Document required environment variables

lib/md_tools.sh

@@ -277,15 +277,24 @@ construct_mdq_url () {
 #
 #   entityID registrarID
 #
-# where entityID is the value of the ./@entityID XML attribute. The 
-# entityID is guaranteed to be non-null.
+# where entityID is the value of the ./@entityID XML attribute. 
+# Assuming the XML is schema-valid, the entityID is guaranteed to 
+# be non-null.
 #
 # The registrarID is the value of the following XML attribute:
 #
 #   ./md:Extensions/mdrpi:RegistrationInfo/@registrationAuthority
 #
 # Since the mdrpi:RegistrationInfo element is an optional element,
 # the registrarID may be null.
+#
+# Environment Variables
+#
+# Two environment variables are required. The LIB_DIR environment
+# variable points to a source code library containing bash scripts,
+# XSLT scripts, and other source files. The TMPDIR environment 
+# variable points to a temporary directory used by this function.
+#
 #######################################################################
 extractIdentifiers () {
 
@@ -382,8 +391,9 @@ extractIdentifiers () {
 #
 #   entityID DisplayName OrganizationName OrganizationDisplayName registrarID
 #
-# where entityID is the value of the ./@entityID XML attribute. The 
-# entityID is the only field guaranteed to be non-null.
+# where entityID is the value of the ./@entityID XML attribute. 
+# Assuming the XML is schema-valid, the entityID is guaranteed to 
+# be non-null.
 #
 # The DisplayName field is the value of the following XML element:
 #
@@ -407,6 +417,14 @@ extractIdentifiers () {
 #
 # Since the mdrpi:RegistrationInfo element is an optional element,
 # the registrarID may be null.
+#
+# Environment Variables
+#
+# Two environment variables are required. The LIB_DIR environment
+# variable points to a source code library containing bash scripts,
+# XSLT scripts, and other source files. The TMPDIR environment 
+# variable points to a temporary directory used by this function.
+#
 #######################################################################
 extractIdPNames () {
 
@@ -522,6 +540,14 @@ extractIdPNames () {
 # which case the endpoint is a so-called IdP SSO endpoint.
 #
 # A return code > 1 is a fatal error.
+#
+# Environment Variables
+#
+# Two environment variables are required. The LIB_DIR environment
+# variable points to a source code library containing bash scripts,
+# XSLT scripts, and other source files. The TMPDIR environment 
+# variable points to a temporary directory used by this function.
+#
 #######################################################################
 listEndpoints () {