Shell script: Define a variable within an if-statement

Question

In a shell program, I would like to define a month variable within an if-statement as below. But I cannot seem to define a variable within the if-statement -- I keep geting an error message that says "command 'dmonth' not found." Any help will be much appreciated!

    #Enter date:

    echo "Enter close-out date of MONTHLY data (in the form mmdd): "
    read usedate
    echo " "

    #Extract first two digits of "usedate" to get the month number:

    dmonthn=${usedate:0:2}
    echo "month number = ${dmonthn}"
    echo " "

    #Translate the numeric month identifier into first three letters of month:

    if [ "$dmonthn" == "01" ]; then
        dmonth = 'Jan'
    elif [ "$dmonthn" == "02" ]; then 
        dmonth = "Feb" 
    elif [ "$dmonthn" == "03" ]; then 
        dmonth = "Mar" 
    elif [ "$dmonthn" == "04" ]; then 
        dmonth = "Apr" 
    elif [ "$dmonthn" == "05" ]; then 
        dmonth = "May" 
    elif [ "$dmonthn" == "06" ]; then 
        dmonth = "Jun" 
    elif [ "$dmonthn" == "07" ]; then
        dmonth = "Jul" 
    elif [ "$dmonthn" == "08" ]; then 
        dmonth = "Aug" 
    elif [ "$dmonthn" == "09" ]; then 
        dmonth = "Sep" 
    elif [ "$dmonthn" == "10" ]; then 
        dmonth = "Oct"
    elif [ "$dmonthn" == "11" ]; then 
        dmonth = "Nov"
    else 
        dmonth = "Dec" 
    fi

    echo dmonth

Barton Chittenden · Accepted Answer · 2014-01-10 18:21:34Z

5

I think that you're having trouble with white space ... it's significant in Bourne shell and it's dirivitives. dmonth="Dec" is an assignment, wheres dmonth = "Dec" is a command with '=' and 'Dec' as arguments.

answered Jan 10, 2014 at 18:21

Barton Chittenden

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that other guy · Accepted Answer · 2014-01-10 18:21:40Z

2

As shellcheck would tell you, you can't use spaces around the = in assignments.

Instead of dmonth = 'Jan', use dmonth='Jan'.

To make the code prettier, you could use an array and index it:

dmonthn=09
months=( Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec )
dmonth=${months[$((10#$dmonthn-1))]}
echo "$dmonth"

or a case statement:

case $dmonthn in
  01) dmonth='Jan' ;;
  02) dmonth='Feb' ;;
  03) dmonth='Mar' ;;
  ...
esac

answered Jan 10, 2014 at 18:21

that other guy

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