#!/bin/bash
#<pre><b>
# Script     : sortnpref
# Version    : 1.0
# Author     : Roland Rashleigh-Berry
# Date       : 26-Apr-2004
# Purpose    : Production script to sort a list using a numeric prefix as the
#              main key.
# SubScripts : none
# Notes      : This utility must be piped into.
#
#              Strings of the form ABCnn_XXX.xx are sorted using the number nn
#              as the main key and the whole string as the secondary key. Only
#              numeric digits immediately preceding the underscore in the 
#              string will be used as the main sort key such that s3d45_meds.sas
#              will have 45 as the main sort key and 3 will not play a part.
#
#              If the string has more than one underscore in the name then only
#              the characters up to the first underscore are used to determine
#              the first sort key such that s11_f88_meds.sas will use the number
#              11 as the main sort key and not 88.
#
# Usage      : ls *[0-9]_*.sas | sortnpref
#===============================================================================
# PARAMETERS:
#-pos- -------------------------------description-------------------------------
# N/A  This utility must be piped into. There are no parameters.
#===============================================================================
# AMENDMENT HISTORY:
# init --date-- mod-id ----------------------description------------------------
# 
#===============================================================================
# This is public domain software. No guarantee as to suitability or accuracy is
# given or implied. User uses this code entirely at their own risk.
#===============================================================================


gawk -F_ '{ # use "_" as the field separator

# find where we get a numeric match at the end of the first field
pos=match($1,/[0-9]*$/)       

# Use RSTART and RLENGTH to extract the matching number and add 0
# to force it to be numeric.
num=substr($1,RSTART,RLENGTH)+0  

# print the number (minimum 5 digits preceeded with zeros) and the original
printf "%0#5d %s\n",num,$0

# sort the list then drop the first numeric field to leave the original 
}' | sort | cut -d' ' -f2-