====== Linux ======

===== Manipulation sur les dates =====
\\ 
==== Commande 'date' ====
  * **Syntaxe** :
<code bash> $ date [+[format_options]]</code>
  * **Exemples** :
<code bash> $ date
 Wed Jul 20 16:49:15 CEST 2022

 $ date +%Y-%m-%d
 2022-07-20</code>
  * **Options de formatage**

^Format	^Description ^
|+%a	|Gives name of the weekday [Mon, Sun, Fri] |
|+%A	|Gives name of the weekday [Monday, Sunday, Friday] |
|+%b	|Gives name of the month [Jan, Feb, Mar] |
|+%B	|Gives name of the month [January, February, March] |
|+%d	|Displays day of the month [05] |
|+%D	|Displays current date MM/DD/YY format [11-01-21] |
|+%F	|Shows date in YYYY-MM-DD format [2021-11-01] |
|+%H	|Shows hour in 24-hour format [22] |
|+%I	|Shows hour in 12-hour format [11] |
|+%j	|Displays the day of the year [001 – 366] |
|+%m	|Displays the number of the month [01-12] |
|+%M	|Displays minutes [00-59] |
|+%S	|Displays seconds [00-59] |
|+%N	|Displays in Nanoseconds |
|+%T	|Displays time as HH:MM:SS [in 24-hour format] |
|+%u	|Day of the week [1-7] 1 is Monday, 6 is Saturday |
|+%U	|Shows week number of the year [00-53] |
|+%Y	|Displays year YYYY [2021] |
|+%Z	|Displays Time zone |

^Format	(avec indicateur)^Description ^
|-d "Yesterday"	|Print yesterday's date and time. |
|-d "tomorrow"	|Print Tomorrow date and time. |
|-d "tomorrow -10 days"	|Find what is the date and time before 10 days from now. |
|-d "last month" "%B"	|Find last month. |
|-d "next month" "%B"	|Find next month. |
|-d "last year" "+%Y"	|Find last year. |
|-d "next year" "+%Y"	|Find next year. |
|-d "Today +2 days" "+%A"	|Forecast the weekday |

\\ 
==== Afficher la date depuis un timestamp ====
<code bash> $ date -d @1381764199
 Mon Oct 14 17:23:19 CEST 2013
</code>
\\ 
==== Nombre de jours entre 2 dates données ====
<code bash>
 $ echo $(( ( $(date -d "2022-07-20" "+%s") - $(date -d "2022-01-01" "+%s") ) / 86400))
 199
 # ou
 $ echo $(($((`date +%s --date 01/10/2016`-`date +%s --date 01/10/2015`))/86400)) jours
 365 jours
</code>
\\ 
==== Identifier une année bissextile ====
<code bash>
 $ for y in {2000..2010}; do date -d $y-02-29 &>/dev/null && echo "$y est bissextile"; done
 2000 est bissextile
 2004 est bissextile
 2008 est bissextile
</code>
\\ 
==== Modifier la date et l'heure du système ====
<code bash>
 $ date --set="Thu Nov 12 13:06:59 IST 2020"
 Thu Nov 12 13:06:59 IST 2020
 $ hwclock --systohc      # synchronise le changement avec l'horloge matérielle
</code>
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