KSH Leap Year Calculation

[SamBones]

OK, OK, I know it's been beaten to death, but I came up with a cool way to test for leap year in Korn Shell.

#!/bin/ksh

typeset -i IS_LEAP=$( cal 2 $(date '+%Y') | grep 29 | wc -l )

(( IS_LEAP )) && print "This is a leap year!"

if (( ! IS_LEAP ))
then
    print "NOT a leap year!"
fi

Basically it uses '[tt]cal[/tt]' to get a calendar of February of this year (simple mod to get other years), [tt]grep[/tt]s that one month calendar for a '29', then counts how many rows the grep output. If it's a leap year, IS_LEAP will equal 1. If it's not a leap year, IS_LEAP will be a 0. So IS_LEAP can be used as a boolean as in the example code.

 

[daPeach]

hi,

there's not much of "kshisms".
this almost could be (arithmetic evaluation excepted, and variable's typing that is not essential) a POSIX script as well.

the script is fine, not the title of the subject.

 

[stefanhei]

Nice, but it will fail in 13 years. Put a tail between cal and grep to get rid of the year in the header that may cause problems.

 

[SamBones]

daPeach: Yup, you're correct.

stefanhei: Good point. Didn't think it through I guess.

#!/bin/ksh

typeset -i IS_LEAP=$( cal 2 $(date '+%Y') | tail -2 | grep 29 | wc -l )

(( IS_LEAP )) && print "This is a leap year!"

if (( ! IS_LEAP ))
then
    print "NOT a leap year!"
fi