Write usage/errors to stderr

.gitignore

@@ -8,6 +8,7 @@
 *.dll
 *.so
 *.dylib
+main
 
 # Test binary, built with `go test -c`
 *.test

main.go

@@ -6,7 +6,19 @@ import (
   "os"
 )
 
+func usage(code int, err error) {
+  if err != nil {
+    os.Stderr.WriteString(fmt.Sprintf("error %s\n", err))
+  }
+  os.Stderr.WriteString(fmt.Sprintf("usage: %s [uri] [bind_dn] [bind_pw] [base_dn] [uid]\n", os.Args[0]))
+  os.Exit(code)
+}
+
 func main() {
+  if len(os.Args) != 6 {
+    usage(1, nil)
+  }
+
   var ldap_uri string      = os.Args[1]
   var ldap_bind_dn string  = os.Args[2]
   var ldap_bind_pw string  = os.Args[3]
@@ -15,19 +27,20 @@ func main() {
 
   l, err := ldap.DialURL(ldap_uri)
   if err != nil {
-    panic(err)
+    usage(2, err)
   }
 
   defer l.Close()
+
   err = l.Bind(ldap_bind_dn, ldap_bind_pw)
   if err != nil {
-    panic(err)
+    usage(3, err)
   }
 
   search_request := ldap.NewSearchRequest(ldap_base_dn, ldap.ScopeWholeSubtree, ldap.NeverDerefAliases, 0, 0, false, fmt.Sprintf("(&(objectClass=posixAccount)(uid=%s))", uid), []string{"dn", "sshPublicKey"}, nil)
   sr, err := l.Search(search_request)
   if err != nil {
-    panic(err)
+    usage(4, err)
   }
 
   for _, entry := range(sr.Entries) {