shell 脚本 : Define a variable within an if-statement

Question

在 shell 程序中，我想在 if 语句中定义一个月份变量，如下所示。但我似乎无法在 if 语句中定义变量——我不断收到一条错误消息，提示“未找到命令‘dmonth’”。任何帮助都感激不尽!

    #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

Answer 1

我认为您在使用空格时遇到了麻烦……它在 Bourne shell 中很重要，而且它是指令。 dmonth="Dec" 是一个赋值，其中 dmonth = "Dec" 是一个以 '=' 和 'Dec' 作为参数的命令。