#!/bin/bash

name="$1"

if [[ "X${name}" == 'X' ]]
 then
    echo "Usage: $0 file-name-snippet"
    exit
 fi

# unwanted.log.25.gz
ls -1 ${name}.[0-9]*.gz | while read file
 do
    extra=$(echo ${file} | sed "s/^${name}.//" | sed 's/.gz$//')
    new=$(date '+%Y%m%d' -d "-${extra} days")
    echo "mv ${file} ${name}-${new}.gz"
    mv ${file} ${name}-${new}.gz
 done