block_website_time

#!/bin/bash
# block_website_time
# block websites by time of day
# run as a cron job, initially i ran this once a minute
# but then tried once every ten minutes... which means i can manually
# edit the hosts file and get a short window of access.
# too easy though, so now it's once every 5 minutes.

# this is the 2nd main version. the main difference from the initial
# version is the chunk of entries this script generates is deleted
# and recreated on every run. the initial version used sed to search
# and replace make comment out entries (or not) when unblocked (or not)
# which meant the script could be more easily circumnavigated.
# this can still be circumnavigated, it's not meant as security, it's
# for personal use by people who *want* a mechanism to reduce their
# time on specific websites.

# -----------------------
# options

hostsfile="$HOME/hoststest"

websites=(  "facebook.com"
            "instagram.com"
            "youtube.com" )

blocktimes=("00:00 08:30"
            "09:30 12:30"
            "13:30 16:30"
            "17:30 20:30"
            "21:30 23:30" )

# end of options

# ---------------------------------------
# function in_time_range
# option --time "hh:mm" - override use of system time with time specified
# option --result "variable" - specify variable name to store range of test
# (it will store an inbetween range if test is negative) - check return result
# return result is 1 if test positive, otherwise 0.
# specify a range as two hour/minute time values, ie: 09:45 12:15
# multiple ranges may be specified at once

function in_time_range()
{
    while [[ $# -gt 0 ]]; do
      case "$1" in
        --time)     checktime="$2" ; shift ;;
        --result)   result="$2"    ; shift ;;
        *) break ;;
      esac
      shift
    done

    if [[ $# -lt 2 ]]; then
        echo "invalid number of parameters for time range."
        exit -1
    fi

    if [[ -z $checktime ]]; then
        checktime=$(date +"%H:%M")
    fi

    currtime=$(date +%s --date="$checktime")
    unset secsm1

    while [[ $# -gt 0 ]]; do
        if [[ $# -eq 1 ]]; then
            echo "unpaired number of start/end times."
            exit -1
        fi
        start="$1"
        secs0=$(date +%s --date="$1")
        shift
        end="$1"
        secs1=$(date +%s --date="$1")
        shift

        if [[ $currtime -ge $secs0 && $currtime -le $secs1 ]]; then
            if [[ -n $result ]]; then
                declare -n ret=$result
                ret="$start $end"
            fi
            return 1
        elif [[ -n $secsm1 && -n $result ]]; then
            # determine if between previous range and this range
            if [[ $currtime -ge $secsm1 && $currtime -le $secs0 ]]; then
                declare -n ret=$result
                ret="$m1time $start"
                return 0
            fi
        fi
        m1time="$end"
        secsm1="$secs1"
    done
    return 0
}

function create_block_list()
{
    echo "# $scriptmd5tag"
    echo "# Any manual edits should be added before the # MD5 line above."
    echo "# Anything added after it could get deleted."
    echo

    block="# "
    in_time_range --result range ${blocktimes[*]}

    if [[ $? -eq 1 ]]; then
        block=""
    fi

    block="${block}127.0.0.1"

    for i in ${websites[@]}; do
        echo "$block $i"
        echo "$block www.$i"
    done

    echo
    echo "# block times for websites:"

    for i in "${blocktimes[@]}"; do
        echo "# $i"
    done

    echo
    echo "# last updated "$(date +"%H:%M")

    return 0
}


# --------------------------------------------------
# start of main processing
# sanity checking...
if [[ ${#websites[@]} -eq 0 ]]; then
    echo "website array undefined"
    exit -1
fi

if [[ ${#blocktimes[@]} -eq 0 ]]; then
    echo "block times array undefined"
    exit -1
fi

script=$0
scriptmd5tag=$(md5sum --tag $script)

sed '/^# MD5 (.*'$(basename $script)')/,$d' -i $hostsfile
create_block_list >> $hostsfile

exit 0