讀書筆記之101個腳本之No.7

今兒個講得是判斷輸入的日期是否正確,有利用到我們之前03這個例子中的函數

下面是代碼

#!/bin/sh
# valid-date -- Validates a date, taking into account leap year rules.

exceedsDaysInMonth()
{

case $(echo $1|tr '[:upper:]' '[:lower:]') in
jan* ) days=31 ;; feb* ) days=28 ;;
mar* ) days=31 ;; apr* ) days=30 ;;
may* ) days=31 ;; jun* ) days=30 ;;
jul* ) days=31 ;; aug* ) days=31 ;;
sep* ) days=30 ;; oct* ) days=31 ;;
nov* ) days=30 ;; dec* ) days=31 ;;
* ) echo "$0: Unknown month name $1" >&2; exit 1
esac

if [ $2 -lt 1 -o $2 -gt $days ] ; then
return 1
else
return 0 # the day number is valid
fi
}

isLeapYear()
{

year=$1
if [ "$((year % 4))" -ne 0 ] ; then
return 1 # nope, not a leap year
elif [ "$((year % 400))" -eq 0 ] ; then
return 0 # yes, it's a leap year
elif [ "$((year % 100))" -eq 0 ] ; then
return 1
else
return 0
fi
}

## Begin main script

if [ $# -ne 3 ] ; then
echo "Usage: $0 month day year" >&2
echo "Typical input formats are 8 3 2002" >&2
exit 1
fi

# Normalize date and split back out returned values


if [ $? -eq 1 ] ; then
exit 1 # error condition already reported by normdate
fi

monthnoToName()
{
# Sets the variable 'month' to the appropriate value
case $1 in
01|1 ) monthd="Jan" ;; 02|2 ) monthd="Feb" ;;

03|3 ) monthd="Mar" ;; 04|4 ) monthd="Apr" ;;
05|5 ) monthd="May" ;; 06|6 ) monthd="Jun" ;;
07|7 ) monthd="Jul" ;; 08|8 ) monthd="Aug" ;;
09|9 ) monthd="Sep" ;; 10) monthd="Oct" ;;
11) monthd="Nov" ;; 12) monthd="Dec" ;;
* ) echo "$0: Unknown numeric month value $1" >&2; exit 1
esac
return 0
}

monthnoToName $1

month="$monthd"
day="$2"
year="$3"

if ! exceedsDaysInMonth $month "$2" ; then
if [ "$month" = "Feb" -a "$2" -eq "29" ] ; then
if ! isLeapYear $3 ; then
echo "$0: $3 is not a leap year, so Feb doesn't have 29 days" >&2
exit 1
fi
else
echo "$0: bad day value: $month doesn't have $2 days" >&2
exit 1
fi
fi

echo "Valid date: $newdate"

exit 0

分析：

1）首先判斷用戶輸入的參數個數是否正確,接著case $1 in 語句判斷月份是否合理.

2）monthnoToName 函數之前出現在我們之前的第03個腳本案例中,用來轉換輸入的數字日期為字元串.

3） exceedsDaysInMonth 用來判斷天數是否超過對應月的最大天數,緊跟著 if [ "$month" = "Feb" -a "$2" -eq "29" ] ; then if ! isLeapYear $3 ; then 用來判斷閏年2月的特殊情況

4）總體的感覺是腳本還是很緊湊的,特別是在判斷閏年與2月的關係的那段代碼,有點意思.

本文出自 「你就當我是浮誇吧」 博客,請務必保留此出處http://2804976.blog.51cto.com/2794976/592622

Tags: linux system 系統