#!/usr/bin/env bash
set -eo pipefail

if [[ "$1" == "-h" || "$1" == "--help" ]]; then
    cat <<EOF
Usage: $(basename "$0") [-h] <lineno> <file>

Display a specific line from a file.

Options:
    -h, --help    Show this help message

Arguments:
    lineno        Line number to display (1-based)
    file          File to read from

EOF
    exit 0
fi

lineno="$1"; shift

if [[ ! -t 0 ]]; then # Read from stdin (pipe)
    sed -n "${lineno}p"
else # Read from file
    sed -n "${lineno}p" -- "$@"
fi