diff --git a/cli/cli.go b/cli/cli.go
new file mode 100644
index 0000000..43ef3f7
--- /dev/null
+++ b/cli/cli.go
@@ -0,0 +1,26 @@
+// Package cli provides utilities for writing command line utilities that
+// interact with services.
+package cli
+
+import "os"
+import "fmt"
+import "flag"
+import "strings"
+
+// Sayf is like Printf, but prints the program name before the message. This is
+// used for printing messages and errors.
+func Sayf (format string, values ...any) {
+	Printf(os.Args[0] + ": " + format, values...)
+}
+
+// Printf prints to stderr.
+func Printf (format string, values ...any) {
+	fmt.Fprintf(flag.CommandLine.Output(), format, values...)
+}
+
+// ServiceUser returns the system user that corresponds to the given service
+// name. This is not necissarily equivalent Hnakra user, although it is good
+// practice to have a 1:1 correspondance between them.
+func ServiceUser (service string) string {
+	return "hn-" + strings.ToLower(service)
+}