#!/bin/sh --
# btrace - convert addr2line output into annotated backtrace

context=${1:-3}

while IFS=: read -r file lineno _; do
    printf '%s\n' "$file"

    if [ -e "$file" ]; then
        awk -v line="$lineno" -v ctx="$context" '
            NR > line - ctx && NR != line && NR < line + ctx { print " ", $0 };
            NR == line { printf "=>%s\n", $0 }
        ' "$file"
    fi
done