When working with date calculations in Linux, you'll often need to determine which week of the month a particular date falls into. While the date command provides week numbers relative to the year (%V for ISO week numbers or %W for week numbers starting from 00), it doesn't have a built-in way to calculate weeks within a month.

The most straightforward approach is to use basic arithmetic with the day of the month:

day=$(date +%d)
week_number=$(( ($day - 1) / 7 + 1 ))
echo "Current week of month: $week_number"

Here's a more compact one-liner using the date command:

echo "Week $((($(date +%-d)-1)/7+1)) of $(date +%B)"

For more complex scenarios where you need to handle different week-starting days, here's a bash function:

get_week_of_month() {
    local day=$(date -d "$1" +%-d)
    local first_day=$(date -d "$1" +%u)
    local offset=$(( (first_day - 1) % 7 ))
    local week_number=$(( (day + offset - 1) / 7 + 1 ))
    echo $week_number
}

Usage example:

get_week_of_month "2023-11-15"

For systems that have ncal installed, you can use this approach:

current_day=$(date +%d)
week_count=1
ncal -b | grep -v "^$" | tail -n +2 | while read line; do
    if [[ $line =~ $current_day ]]; then
        echo "Week $week_count"
        break
    fi
    ((week_count++))
done

Consider these special cases in your implementation:

• Months that start on Sunday
• Last week might have fewer than 7 days
• Localization and timezone considerations

For systems without GNU date (like macOS), use this portable version:

day=$(date +%e | xargs) # xargs trims whitespace
week_number=$(( (day - 1) / 7 + 1 ))
echo $week_number

When working with date calculations in Linux, you might need to determine which week of the month a particular day falls into. For example, days 1-7 would be week 1, days 8-14 week 2, and so on. While the standard date command provides week numbers relative to the year (%U or %W), it doesn't directly offer a week-of-month calculation.

Here's a straightforward way to calculate the week number of the month:

day=$(date +%d)
week_num=$(( (day - 1) / 7 + 1 ))
echo "We're in week $week_num of the month"

For a more robust solution that handles the last week correctly (which might have fewer than 7 days), you could use:

day=$(date +%d)
week_num=$(( (day + 6) / 7 ))
echo "Current week of month: $week_num"

For frequent use in scripts, you might want to create a shell function:

get_week_of_month() {
    local day=$(date -d "$1" +%d 2>/dev/null || date +%d)
    echo $(( (day + 6) / 7 ))
}

# Usage examples:
get_week_of_month             # current date
get_week_of_month "2023-11-15" # specific date

If you have GNU date (common on Linux systems), you can use this more compact version:

date -d "+$(($(date +%d)-1)) days" +%U | awk '{print $1-'"$(date -d "-$(($(date +%d)-1)) days" +%U)"'+1}'

The solutions above assume weeks start on Sunday. If you need Monday as the first day, you might need to adjust the calculation based on the weekday of the first day of the month.

While Linux doesn't provide a direct way to get the week-of-month number, simple arithmetic with the day-of-month value gives you reliable results for most use cases. The methods shown here are lightweight and suitable for scripting purposes.