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Top Forums Shell Programming and Scripting meaning of today=${1:-${today}} Post 302612729 by balajesuri on Monday 26th of March 2012 09:44:13 AM
Old 03-26-2012
If a parameter is given along with a script name while invoking it, then that parameter is considered, otherwise 'today' would contain `date +%y%m%d`.

For e.g., consider this script:
Code:
#! /bin/bash
today=`date '+%y%m%d'`
today=${1:-${today}}
echo $today

While invoking it, if you provide a parameter then variable 'today' would contain that parameter:
Code:
[user@host ~]$ ./test.sh 120331
120331

If you invoked the script without any parameters, then variable 'today' would hold today's date:
Code:
[user@host ~]$ ./test.sh
120326

This User Gave Thanks to balajesuri For This Post:
 

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Date::Manip::Migration5to6(3)				User Contributed Perl Documentation			     Date::Manip::Migration5to6(3)

NAME
Date::Manip::Migration5to6 - how to upgrade from 5.xx to 6.00 SYNOPSIS
When upgrading from Date::Manip 5.xx to 6.00, a few changes may be necessary to your scripts. The Date::Manip::Changes5to6 document lists in more detail the ways in which Date::Manip changed, but very few of these actually entail changes to your script. It should be noted that once the changes are made to your script, it will no longer run correctly in 5.xx. NECESSARY AND SUGGESTED CHANGES
The following changes are necessary, or strongly suggested: Reading config files with Date_Init If you use Date_Init to read any config files (if you do business mode calculations, you probably do), you should remove all of the following config variables from your call to Date_Init: GlobalCnf=FILE PersonalCnf=FILE PathSep=* IgnoreGlobalCnf=* PersonalCnfPath=* and replace them with: ConfigFile=FILE where FILE is now the full path to a config file. Also, the ConfigFile argument should be the first argument in Date_Init. Date_ConvTZ The Date_ConvTZ function has changed. It should now take 3 arguments: $date = Date_ConvTZ($date,$from,$to); If $from is not given, it defaults to the local time zone. If $to is not given, it defaults to the local time zone. The date is converted from the $from time zone into the $to time zone. Both should be any time zone (or alias) supported by Date::Manip. The old $errlevel argument is no longer handled. ConvTZ and TZ config variables If you use either the ConvTZ or TZ config variables, you should replace them with either SetDate or ForceDate. See the Date::Manip::Config document for information. Other deprecated config variables Most of the deprecated config variables continue to function (though they will be removed at a future date). These include: GlobalCnf IgnoreGlobalCnf PersonalCnf PersonalCnfPath PathSep TZ Internal The following variables have been removed. If you use any of them, you may need to modify your scripts: ConvTZ TodayIsMidnight DeltaSigns UpdateCurrTZ today, yesterday, tomorrow If you parse the strings "today", "yesterday", or "tomorrow" in order to get the time now, or 24 hours in the past/future, this will no longer work. These strings now refer strictly to the date (so "today" is the current day at midnight, "yesterday" is the previous day at midnight, etc.). To get the time now, 24 hours ago, or 24 hours in the future, you would need to parse the strings "now", "-24:00:00", or "+24:00:00" respectively. Do not use Memoize In 5.xx, it was documented that you could use the module Memoize to speed up Date::Manip, especially when sorting dates. This information is no longer accurate. Using Memoize in conjuction with Date::Manip should have little impact on performance, and may lead to incorrect results, especially if you change config variables. Please see the Date::Manip::Changes5to6 (GENERAL CHANGES) document for more information. If you find other instances where it is necessary to modify your script, please email me so that I can add that information to this document. BUGS AND QUESTIONS
Please refer to the Date::Manip::Problems documentation for information on submitting bug reports or questions to the author. SEE ALSO
Date::Manip - main module documentation LICENSE
This script is free software; you can redistribute it and/or modify it under the same terms as Perl itself. AUTHOR
Sullivan Beck (sbeck@cpan.org) perl v5.12.1 2010-01-12 Date::Manip::Migration5to6(3)
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