Show nth line with context 5 of each file

sl.sh

#!/bin/bash

#
# Show nth line with context 5 of each file
#

show_lines ()
{
    local file n ctx min max lineno star
    file=${1}
    n=${2}
    ctx=${3}

    min=$((n-ctx))
    if [[ ${min} -le 0 ]]; then
        min=1
    fi
    max=$((n+ctx))

    printf "${file}: \n"
    lineno=${min}
    sed -n -e "${min},${max}p" "${file}" | while read LINE; do
        if [[ ${lineno} == ${n} ]]; then
            star="*"
        else
            star=" "
        fi
        printf "%s%d:\t%s\n" "${star}" ${lineno} "${LINE}"
        lineno=$((lineno+1))
    done
    printf "\n"
}

N=${1}
shift 1

while [[ -n "${1}" ]]; do
    show_lines "${1}" ${N} 5
    shift 1
done