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  • tech0x20 6:18 pm on September 24, 2011 Permalink | Reply
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    perl script to generate a list of Julian day/day of year dates, given start and end. 

    I discovered myself on a unix system with a ‘date’ utility that only accepts the -u and + parameters, a fairly basic perl install, and lots of archives that are listed by the “Julian day” (day of year) date.

    I put together a perl script using the functions I had at my disposal. The script below makes some allowance for a few different formats, but not nearly as much as Date::Manip would have given me. Feedback appreciated.

    use Time::Local;
    use Getopt::Long;
    use strict;
    sub getJJJFromParameter
    	my $dateString = shift; 
    	our $mm;
    	our $dd;
    	our $yyyy;
    	if($dateString =~ m/d{1,2}/d{1,2}/d{2,4}/) {
    		($mm, $dd, $yyyy) = split(///, $dateString);
    	} elsif ($dateString =~ m/d{2,4}-d{1,2}-d{1,2}/) {
    		($yyyy, $mm, $dd) = split(/-/, $dateString);
    	} elsif ($dateString =~ m/d{1,2}-d{1,2}-d{2,4}/) {
    		($mm, $dd, $yyyy) = split(/-/, $dateString);
    	$yyyy %= 100;
    	$yyyy += 100;
    	my @dt = localtime(timelocal(0,0,0,$dd,$mm-1,$yyyy));
    # main script
    my $startDate='';
    my $endDate='';
    my $startJJJ = 0;
    my $endJJJ = 0;
    GetOptions('start=s' => $startDate, 'end=s' => $endDate);
    if ($startDate == '') {
    } else {
    	$startJJJ = getJJJFromParameter($startDate); 
    if ($endDate != '') {
    	$endJJJ = getJJJFromParameter($endDate); 
    } else {
    	$endJJJ = $startJJJ;
    my $jjj;
    printf "%03d to %03dn", $startJJJ, $endJJJ;
    for ($jjj=$startJJJ; $jjj <= $endJJJ; $jjj++) {
    	printf("%03d ", $jjj);
  • tech0x20 3:53 pm on March 21, 2011 Permalink | Reply
    Tags: , , ,   

    Date formatting for Single Unix Specification(R) versions of “date” 

    The date command is wonderful for formatting dates, as such

    date --date="2010-01-01" +%Y%j

    But what happens when you’re on a system whose date command only supports the -u [UTC] and + [for formatting] options?

    Below is a quick hack in straight C that provides the ability to format a date that you provide. This is ideal if your unix install of perl is very basic or non-existent, but you still have access to the C compiler.

    Compiling the target would go as follows:

    gcc strptime.c -o strptime

    Running the output would be as follows:

    ./strptime "2010-01-01" "%Y%j"

    strptime.c source code–Please note: there is limited error checking for the wrong arguments, etc., and overlapping a built-in name such as strptime() isn’t the best of practices…

    int main(int argc, char *argv[]) {
        struct tm tm;
        time_t t;
        char string[255];
        if(strptime(argv[1], "%Y-%m-%d", &tm) == NULL) {
            if (strptime(argv[1], "%m/%d/%Y", &tm) == NULL ) {
                fprintf(stderr, "format errorn");
                return 1;
        strftime(string, sizeof(string) - 1, argv[2], &tm);
        return 0;
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