#!/bin/bash
s="1.mapped.bam 2.mapped.bam 3.mapped.bam"
sed -E 's/([0-9]+)\.mapped\.bam/SAMPLE_\1/g' <<< "$s"
sed 's/\([0-9][0-9]*\)\.mapped\.bam/SAMPLE_\1/g' <<< "$s"
IyEvYmluL2Jhc2gKcz0iMS5tYXBwZWQuYmFtCTIubWFwcGVkLmJhbQkzLm1hcHBlZC5iYW0iCnNlZCAtRSAncy8oWzAtOV0rKVwubWFwcGVkXC5iYW0vU0FNUExFX1wxL2cnIDw8PCAiJHMiCnNlZCAncy9cKFswLTldWzAtOV0qXClcLm1hcHBlZFwuYmFtL1NBTVBMRV9cMS9nJyA8PDwgIiRzIg==