How to get the last 'N' business days in a Unix shell script using a `for` loop?

Question

The following script:

N=5
BUSINESS_DATE=`date -d "-2 day" +"%Y%m%d"`
for (( c=0; c<N ; c++ ))
do
    WEEKDAY=`date --date="$BUSINESS_DATE -$c day" +%w`

    if [ $WEEKDAY == "0" ]
    then
        FILE_DT_TMP=`date --date="$BUSINESS_DATE -$c day-2day" +%Y%m%d`;
    elif [ $WEEKDAY == "6" ]
    then
        FILE_DT_TMP=`date --date="$BUSINESS_DATE -$c day -2day" +%Y%m%d`;
    elif [ $WEEKDAY == "5" ]
    then
        FILE_DT_TMP=`date --date="$BUSINESS_DATE -$c day -2day" +%Y%m%d`;
    elif [ $WEEKDAY == "4" ]
    then
        FILE_DT_TMP=`date --date="$BUSINESS_DATE -$c day -2day" +%Y%m%d`;
    elif [ $WEEKDAY == "3" ]
    then
        FILE_DT_TMP=`date --date="$BUSINESS_DATE -$c day -2day" +%Y%m%d`;
    elif [ $WEEKDAY == "2" ]
    then
        FILE_DT_TMP=`date --date="$BUSINESS_DATE -$c day -2day" +%Y%m%d`;
    elif [ $WEEKDAY == "1" ]
    then
        FILE_DT_TMP=`date --date="$BUSINESS_DATE -$c day -2day" +%Y%m%d`;
    else
        FILE_DT_TMP=`date --date="$BUSINESS_DATE -$c day" +%Y%m%d`
    fi
    export FILE_DT=$FILE_DT_TMP
    echo "File date is :$FILE_DT"
done

is not giving proper output.  Can anyone advise me – what’s wrong, and how do I fix it?

Solution 1

If you want just 5 working days before today try:

for d in Mon Tue Wed Thu Fri
do
    date +%Y%m%d -d "last $d"
done | sort

For any N-days before today:

N=10
for i in $(seq $(($N + $N / 5 * 2)) -1 1)
do
    [ `date --date="-$i day" +%u` -le 5 ] &&
       date -d "-$i day" +"File date is : %Y%m%d"
done

Solution 2

I understand you actually want N days listed rather than the hardcoded five you have shown in your question. Here is a bash solution that will address this requirement:

n=5
today=$(date +'%Y-%m-%d')
for ((d=1; n>0; d++))
do
    # Adjust this next line to get the date format you require, e.g. +'%Y%m%d'
    date=$(date --date "$today -$d day")
    nday=$(date --date "$today -$d day" +'%w')
    if [[ nday > 0 && nday < 6 ]]
    then
        # Adjust this next line to output whatever you really need
        echo "n=$n, d=$d, nday=$nday, date=$date: WEEKDAY"
        ((n--))
    fi
done

Output for n=5, run on 5th November 2015

n=5, d=1, nday=3, date=Wed,  4 Nov 2015 00:00:00: WEEKDAY
n=4, d=2, nday=2, date=Tue,  3 Nov 2015 00:00:00: WEEKDAY
n=3, d=3, nday=1, date=Mon,  2 Nov 2015 00:00:00: WEEKDAY
n=2, d=6, nday=5, date=Fri, 30 Oct 2015 00:00:00: WEEKDAY
n=1, d=7, nday=4, date=Thu, 29 Oct 2015 00:00:00: WEEKDAY

Comments

[G-Man Says 'Reinstate Monica']

(0) Format your code so it’s readable.  (garethTheRed and I did that for you, including correcting the spelling of “business”.)  (1) Explain what you want it to do, in the body of the question.  (2) Say what it is doing.  (3) Describe what you have done to solve the problem yourself.

[Costas]

for d in Mon Tue Wed Thu Fri ; do date +%Y%m%d -d "last $d" ; done | sort is not acceptable?

[Alessio]

this doesn't answer your question buy see also the cal command for a nicely formatted printout of the current month (or, with options, several months, or year).

[RobertL]

OK. Thanks. As you can see your example did not work before I made the above changes. It's a little confusing when the example doesn't work.

[srikanth]

Try to get required output na

[srikanth]

Thanks for the formating. i was in a hurrey so could nt do it that way.. Stil i did not get the required output.I want last "n" business days.

[Alessio]

@srikanth was the problem caused by the missing space between day and -2day for the 0 case that i pointed out? edit your question to show an example of the ouput you are getting and an example of the output you expect to get.

[srikanth]

Sorry I want "N" business days not just 5.

[roaima]

@srikanth please edit your question to include this new information. Otherwise we aren't going to know, because the title of your post clearly states FIVE days, and your example code also uses a hard-coded 5.

[Costas]

@srikanth See updated

[Jeff Schaller]

This is the last 5 days, while the question asks for the last five business days. Notice their logic that checks for the day of the week.