yyyymmdd

uses cal Unix program to print out the days in a month

Installation | Usage | Annotated source | License

Installation

You can just copy and paste the yyyymmdd.sh function or do the following

mkdir -p ~/.bash
cd ~/.bash
git clone git://github.com/fibo/yyyymmdd.git

Edit your ~/.bash_profile or ~/.profile and add the following

source ~/.bash/yyyymmdd/yyyymmdd.sh

On MacOS it is required to install coreutils, with brew do

brew install coreutils

Usage

Pass it year and month in YYYYMM format

$ yyyymmdd 201701
20170101
20170102
...
20170129
20170130
20170131

Optionally use FROM and/or UNTIL environment variables, which are passed to date -d GNU command, for example

• UNTIL=now yyyymmdd 201701
• UNTIL=yesterday yyyymmdd 201701
• UNTIL="2 hours ago" yyyymmdd 201701
• UNTIL=20170117 yyyymmdd 201701
• FROM=20170117 yyyymmdd 201701

You can also use both across multiple yyyymmdd command invocation

export FROM=20170117
export UNTIL=now
yyyymmdd 201701
yyyymmdd 201702

Annotated source

Create a yyyymmdd bash function.

function yyyymmdd () {

Then split input into year and month.

    YYYYMM=$1

    if [ ${#YYYYMM} -ne 6 ]
    then
        echo "Param $YYYYMM is required in YYYYMM format" 1>&2
    else
        YYYY=${YYYYMM:0:4}
        MM=${YYYYMM:4:2}

Use gdate on MacOS, and date on Linux. Use cal to output days: on Linux it could highlight current day; option cal -h turns it off but it is not supported, nor necessary on MacOS.

    CAL=$(which cal)

    case "$OSTYPE" in
        darwin*)
            DATE=$(which gdate)
        ;;
        linux*)
            DATE=$(which date)
            CAL="$CAL -h"
        ;;
    esac

Handle FROM and UNTIL optional environment variables

    YYYYMMDD_MIN=0
    YYYYMMDD_MAX=99999999

    if [ ! -z "$FROM" ]
    then
        YYYYMMDD_MIN=`$DATE --date "$FROM" +%Y%m%d`
    fi

    if [ ! -z "$UNTIL" ]
    then
        YYYYMMDD_MAX=`$DATE --date "$UNTIL" +%Y%m%d`
    fi

Loop over days of month

    for DAY in $($CAL $MM $YYYY | grep '^ *[0-9]')
    do
        DD=$(printf "%02d" $DAY)
        YYYYMMDD=$YYYY$MM$DD

        if [ $YYYYMMDD -gt $YYYYMMDD_MIN -a $YYYYMMDD -le $YYYYMMDD_MAX ]
        then
            echo $YYYY$MM$DD
        fi
    done

… and we are done!

    fi
}

License

MIT

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