diff --git a/bash/next.awk b/bash/next.awk
index c5e19c3..e2f93a1 100644
--- a/bash/next.awk
+++ b/bash/next.awk
@@ -1,15 +1,18 @@
 # awk script to increment the digits, preserve the zero prefix, add string descriptor if supplied, and add back extension
 
 BEGIN {
-# set field separator, blank by default
+# Builtin variable, "field seperator", blank by default. The neatness of this is
+# the main reason I use awk to parse the filename.
 FS = "."
 }
 
 {
+
+# another reason why awk is great for this:
 newnum = $1 + 1
-nzeros = length($1) - length(int(newnum))
 
 # could I do this with a simpler regex to select all leading zeros?
+nzeros = length($1) - length(int(newnum))
 leadingzeros = ""
 if (nzeros > 0)
   for (i = 1; i <= nzeros; i++)
diff --git a/bash/rename.awk b/bash/rename.awk
new file mode 100644
index 0000000..b90ed2f
--- /dev/null
+++ b/bash/rename.awk
@@ -0,0 +1,27 @@
+# generates a string of "oldname newname" from 2 records, for use with mv. Main
+# problem solved here generating the newname string using the number prefix and
+# filetype affix.
+
+BEGIN {
+  FS="."
+  oldname = ""
+  num = ""
+  ext = ""
+  newname = ""
+}
+
+NR == 1 {
+  oldname = $0
+  num = $1
+  # important that this is the last field, not numbered, to allow for a file
+  # without a string descriptor.
+  ext = $NF
+}
+
+NR == 2 {
+  newname = sprintf("%s.%s.%s", num, $0, ext)
+}
+
+END {
+  print oldname, newname
+}
diff --git a/bash/rename.sh b/bash/rename.sh
index 2fb9cae..419f42c 100755
--- a/bash/rename.sh
+++ b/bash/rename.sh
@@ -12,32 +12,6 @@
 
 # split the args by a newline so that awk reads them as separate "records"
 mvcmd=`echo "$1
-$2" |
-awk '
-BEGIN {
-  # Builtin variable, "field seperator". The neatness of this is the main reason
-  # I use awk to parse the filename.
-  FS="."
-  oldname = ""
-  num = ""
-  ext = ""
-  newname = ""
-}
+$2" | awk -f $UMBASEPATH/rename.awk`
 
-NR == 1 {
-  oldname = $0
-  num = $1
-  # important that this is the last field, not numbered, to allow for a file
-  # without a string descriptor.
-  ext = $NF
-}
-
-NR == 2 {
-  newname = sprintf("%s.%s.%s", num, $0, ext)
-}
-
-END {
-  print oldname, newname
-}
-'`
 mv $mvcmd