diff --git a/lib/misc.sh b/lib/misc.sh
deleted file mode 100644
index a647895..0000000
--- a/lib/misc.sh
+++ /dev/null
@@ -1,41 +0,0 @@
-# Miscellaneous shell-related functions.
-
-
-# Print boolean value of the exit code of the command passed as argument.
-bool() {
-    "$@" && echo "true" || echo "false"
-}
-
-# Return whether a string is present in a list of strings.
-contains_string() {
-    local match="$1"
-    local strings="$2"
-
-    local s
-    for s in $strings; do
-        if [ "$s" == "$match" ]; then
-            return 0
-        fi
-    done
-    return 1
-}
-
-# Return whether the shell is interactive.
-is_interactive() {
-    [[ $- == *i* ]]
-}
-
-# Source a system file.  If no filename is given, list the available names.
-s() {
-    local sourcedir="$SYSTEM_DIR/source"
-    if [ $# -eq 0 ]; then
-        ls -1 "$sourcedir"
-        return
-    fi
-
-    local file
-    for file in "$@"; do
-        # shellcheck disable=SC1090
-        . "$sourcedir/$file"
-    done
-}
diff --git a/rc.d/210-source.sh b/rc.d/210-source.sh
new file mode 100644
index 0000000..50d76a9
--- /dev/null
+++ b/rc.d/210-source.sh
@@ -0,0 +1,16 @@
+# Helper to source global definition files.
+
+# Source a system file.  If no filename is given, list the available names.
+s() {
+    local sourcedir="$SYSTEM_DIR/source"
+    if [ $# -eq 0 ]; then
+        ls -1 "$sourcedir"
+        return
+    fi
+
+    local file
+    for file in "$@"; do
+        # shellcheck disable=SC1090
+        . "$sourcedir/$file"
+    done
+}
diff --git a/rc.d/300-completion.sh b/rc.d/300-completion.sh
index fbdf58b..de8526e 100644
--- a/rc.d/300-completion.sh
+++ b/rc.d/300-completion.sh
@@ -1,7 +1,7 @@
 # Autocompletion configuration
 
-
-if is_interactive; then
+# only load completion for interactive shells
+if [[ $- == *i* ]]; then
     source_if_exists /etc/bash_completion
 
     _bcomp_s() {