diff --git a/setup.sh b/setup.sh
index b888586..9d5e4a6 100755
--- a/setup.sh
+++ b/setup.sh
@@ -3,7 +3,7 @@ set -e
 
 # setup.sh --- 10sr setup script
 
-__setups="gitconf tmux scripts darwin dirs selfupdate windirs"
+__setups="shrc_common gitconf tmux scripts darwin dirs selfupdate windirs"
 
 __homelocal="$HOME/.local"
 __homevar="$HOME/.var"
@@ -23,41 +23,47 @@ _download(){
 }
 
 
-#############################
-# gen_common
+##################################
+# Detect systems
 
-# Generate ~/.shrc.common, which contains system infos and is sourced from
-# setup.sh (this file) and dotfiles/shrc .
-# This functions is always called.
+detect_systems(){
+    ismsys=false
+    iscygwin=false
+    iswindows=false
 
-# this variable must consistent with shrc
-__shrc_common="$HOME/.shrc.common"
+    isdarwin=false
+    isfreebsd=false
+    isbsd=false
 
-gen_common(){
-    test -f "$__shrc_common" && rm -- "$__shrc_common"
-
-    __ismsys=false
-    __iscygwin=false
-    __iswindows=false
-
-    __isdarwin=false
-    __isfreebsd=false
-    __isbsd=false
-
-    __islinux=false
+    islinux=false
 
     # $OSTYPE is another choice. which is better?
     # NOTE: sh on FreeBSD does not define OSTYPE
     case `uname` in
-        (MINGW*) __ismsys=true ;;
-        (CYGWIN*) __iscygwin=true ;;
-        (Darwin*) __isdarwin=true ;;
-        (FreeBSD*) __isfreebsd=true ;;
-        (Linux*) __islinux=true ;;
+        (MINGW*) ismsys=true ;;
+        (CYGWIN*) iscygwin=true ;;
+        (Darwin*) isdarwin=true ;;
+        (FreeBSD*) isfreebsd=true ;;
+        (Linux*) islinux=true ;;
     esac
-    ($__ismsys || $__iscygwin) && __iswindows=true
+    ($ismsys || $iscygwin) && iswindows=true
     # is this true?
-    ($__isdarwin || $__isfreebsd) && __isbsd=true
+    ($isdarwin || $isfreebsd) && isbsd=true
+    return 0
+}
+
+
+#############################
+# shrc_common
+
+# Generate ~/.shrc.common, which contains system infos and is sourced from
+# setup.sh (this file) and dotfiles/shrc .
+
+# this variable must consistent with shrc
+__shrc_common="$HOME/.shrc.common"
+
+setup_shrc_common(){
+    test -f "$__shrc_common" && rm -- "$__shrc_common"
 
     cat <<__EOC__ >"$__shrc_common"
 #!/bin/sh
@@ -65,15 +71,15 @@ gen_common(){
 # $__shrc_common
 # Automatically generated by $0
 
-ismsys=$__ismsys
-iscygwin=$__iscygwin
-iswindows=$__iswindows
+ismsys=$ismsys
+iscygwin=$iscygwin
+iswindows=$iswindows
 
-isdarwin=$__isdarwin
-isfreebsd=$__isfreebsd
-isbsd=$__isbsd
+isdarwin=$isdarwin
+isfreebsd=$isfreebsd
+isbsd=$isbsd
 
-islinux=$__islinux
+islinux=$islinux
 
 __homelocal="$__homelocal"
 __homevar="$__homevar"
@@ -293,12 +299,11 @@ setup_dirs(){
 
 main(){
 
-    gen_common
-    . "$__shrc_common"
+    detect_systems
 
     if test -z "$1"
     then
-        echo "usage: ./setup.sh <setups> ..."
+        echo "Usage: ./setup.sh <setups> ..."
         echo "setups: all $__setups"
         exit 1
     fi