diff --git a/dotfiles/zshrc b/dotfiles/zshrc
index 26c93e3..e67a20e 100644
--- a/dotfiles/zshrc
+++ b/dotfiles/zshrc
@@ -44,8 +44,10 @@ bindkey '^[[B' history-search-forward
 bindkey '^[[1;5C' forward-word
 bindkey '^[[1;5D' backward-word
 
-# Source extras
-for file in $HOME/.zshrc.d/* ; do source "$file" ; done
+# Source extras if interactive
+if [[ $- == *i* ]] ; then
+  for file in $HOME/.zshrc.d/* ; do source "$file" ; done
+fi
 
 # Load any local settings
 if [ -e $HOME/.zshrc.local ] ; then source $HOME/.zshrc.local ; fi
diff --git a/dotfiles/zshrc.d/assemble.zsh b/dotfiles/zshrc.d/assemble.zsh
new file mode 100644
index 0000000..87431be
--- /dev/null
+++ b/dotfiles/zshrc.d/assemble.zsh
@@ -0,0 +1,17 @@
+if [ -f "`command which nasm`" -a -f "`command which objdump`" ] ; then
+  assemble_shellcode() {
+    if [ -z "$1" ] ; then echo "Usage: $0 <assembly file>" >&2 ; return 1 ; fi
+    local NASM=`command which nasm`
+    local OBJDUMP=`command which objdump`
+    local TMPF=`mktemp`
+    local bytes
+    local byte
+    $NASM -f elf -o $TMPF $1
+    $OBJDUMP -M intel -d $TMPF | grep '^ ' | cut -f2 | while read -A bytes ; do
+      for byte in $bytes ; do
+        echo -n "\\\\x$byte"
+      done
+    done
+    echo
+  }
+fi