![\"Unix](\"\/wp-content\/uploads\/2020\/01\/1b3a3bdeb0400f3b34d5cd6964a48010.jpg\")
<\/p>\nViti 2020 \u00ebsht\u00eb nj\u00eb vit historik p\u00ebr Unix: n\u00eb fillim t\u00eb vitit, sistemi origjinal i operimit mbushi 50 vjet. Koha Unix, e njohur gjithashtu si «data e epok\u00ebs», \u00ebsht\u00eb numri i sekondave t\u00eb kaluara q\u00eb nga 1 Janari 1970. Por \u00e7far\u00eb i shqet\u00ebson zhvilluesit e b\u00ebrtham\u00ebs n\u00eb lidhje me p\u00ebrvjetorin gjysm\u00eb shekullor t\u00eb Unix-it?<\/p>\n
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Megjith\u00ebse disa nga zhvillimet e hershme t\u00eb Unix-i i paraprijn\u00eb fillimit zyrtar t\u00eb «epok\u00ebs» s\u00eb tij, 1 Janari 1970 mbetet pika zero n\u00eb koh\u00eb p\u00ebr POSIX. Prandaj, me fillimin e 1 Janarit 2020, platforma zyrtarisht mbushi plot 50 vjet.<\/p>\n
Koha <\/strong>Unix p\u00ebrball\u00eb koh\u00ebs njer\u00ebzore<\/strong><\/p>\n Nga k\u00ebndv\u00ebshtrimi njer\u00ebzor, 50 vjet \u00ebsht\u00eb nj\u00eb periudh\u00eb e madhe. Nga k\u00ebndv\u00ebshtrimi i koh\u00ebs Unix, nuk ka asgj\u00eb t\u00eb ve\u00e7ant\u00eb n\u00eb 50 vjet, nd\u00ebrsa 43 vjet do t\u00eb ishin po aq t\u00eb r\u00ebnd\u00ebsishme. Sistemet Unix (p\u00ebrfshir\u00eb Linux) ruajn\u00eb vlerat e dat\u00ebs dhe or\u00ebs si numrin e sekondave t\u00eb kaluara nga 1970-01-01 00:00:00 UTC, me regjistrim n\u00eb 32 bit. P\u00ebr t\u00eb p\u00ebrcaktuar sa sekonda kan\u00eb kaluar nga ajo koh\u00eb, dhe k\u00ebshtu vlera aktuale e koh\u00ebs Unix, mund t\u00eb ekzekutoni komand\u00ebn:<\/p>\n $ date +%s<\/p>\n 1576883876<\/p>\n Argumenti %s pas komand\u00ebs date p\u00ebrcakton shfaqjen e dat\u00ebs dhe or\u00ebs aktuale si nj\u00eb num\u00ebr sekondash q\u00eb nga fillimi i 1970-01-01.<\/p>\n Cila \u00ebsht\u00eb data maksimale q\u00eb mund t\u00eb ruaj\u00eb nj\u00eb sistem Unix? <\/strong>Unix?<\/strong><\/p>\n P\u00ebr t\u00eb kuptuar sa koh\u00eb mund t\u00eb ruaj\u00eb nj\u00eb sistem Unix, duhet vler\u00ebsuar kapaciteti i fush\u00ebs 32-bit. Kjo mund t\u00eb llogaritet k\u00ebshtu:<\/p>\n $ echo ‘2^32’ | bc<\/p>\n 4294967296<\/p>\n Megjithat\u00eb, duke qen\u00eb se Unix parashikon ruajtjen e numrave negativ\u00eb, nj\u00eb bit rezervuar p\u00ebr shenj\u00eb, k\u00ebshtu q\u00eb vlera e koh\u00ebs zvog\u00eblohet n\u00eb:<\/p>\n $ echo ‘2^31’ | bc<\/p>\n 2147483648<\/p>\n Dhe duke qen\u00eb se num\u00ebrimi Unix fillon nga 0, kjo do t\u00eb thot\u00eb se kemi 2 147 483 648 vlera, por vlera m\u00eb e madhe \u00ebsht\u00eb 2 147 483 647 \u2014 vlera e dat\u00ebs dhe or\u00ebs Unix nuk mund t\u00eb kaloj\u00eb k\u00ebt\u00eb num\u00ebr. Si\u00e7 \u00ebsht\u00eb nj\u00eb odomet\u00ebr n\u00eb nj\u00eb makin\u00eb q\u00eb nuk mund t\u00eb tregoj\u00eb m\u00eb shum\u00eb se 999 999 kilometra \u2014 shtoni 1 dhe vlera do t\u00eb zerohet.<\/p>\n Sa zgjat nj\u00eb vit n\u00eb sekonda?<\/strong><\/p>\n Numri i sekondave n\u00eb nj\u00eb vit mund t\u00eb llogaritet n\u00eb k\u00ebt\u00eb m\u00ebnyr\u00eb:<\/p>\n $ expr 24 * 60 * 60 * 365<\/p>\n 31536000<\/p>\n N\u00eb nj\u00eb vit t\u00eb shenjt\u00eb shtohet nj\u00eb dit\u00eb tjet\u00ebr:<\/p>\n $ expr 24 * 60 * 60 * 366<\/p>\n 31622400<\/p>\n Si e shfaq Unix dit\u00eblindjen e tij t\u00eb 50-t\u00eb?<\/strong><\/p>\n M\u00eb 1 janar 2020 n\u00eb or\u00ebn 12:00 t\u00eb m\u00ebngjesit do t\u00eb jet\u00eb koha 1577836800. Llogaritja paksa komplikohet, sepse duhet marr\u00eb parasysh vitet e shenjta. Q\u00eb nga fillimi i epok\u00ebs Unix ka pasur 12 t\u00eb till\u00eb, duke filluar nga viti 1972 deri n\u00eb vitin 2016. Pra, ka pasur 38 vite t\u00eb zakonshme.<\/p>\n Kjo \u00ebsht\u00eb komanda expr p\u00ebr t\u00eb llogaritur sekondat p\u00ebr 50 vitet e kaluara:<\/p>\n $ expr 24 * 60 * 60 * 365 * 38 + 24 * 60 * 60 * 366 * 12<\/p>\n 1577836800<\/p>\n Ose ndryshe, duke marr\u00eb parasysh llogaritjet e b\u00ebra m\u00eb par\u00eb:<\/p>\n $ expr 31536000 * 38 + 31622400 * 12<\/p>\n 1577836800<\/p>\n Ky m\u00ebnyr\u00eb e regjistrimit t\u00eb koh\u00ebs e b\u00ebri sistemin Unix t\u00eb pap\u00ebrshkuesh\u00ebm nga problemi Y2K q\u00eb shqet\u00ebsonte njer\u00ebzit n\u00eb fund t\u00eb vitit 1999, t\u00eb cil\u00ebt ishin t\u00eb shqet\u00ebsuar se kalimi n\u00eb vitin 2000 mund t\u00eb d\u00ebmtonte sistemet kompjuterike. Sfidat ishin shum\u00eb m\u00eb pak se sa pritej. N\u00eb t\u00eb v\u00ebrtet\u00eb, vet\u00ebm aplikacionet q\u00eb regjistronin vitet n\u00eb format dyshifror u p\u00ebrball\u00ebn me zerozimin e datave. Shum\u00eb zhvillues b\u00ebn\u00eb pun\u00eb shtes\u00eb p\u00ebr t\u00eb siguruar q\u00eb aplikacionet e tyre t\u00eb mos preken nga problemi Y2K.<\/p>\n Kur \u00ebsht\u00eb koha <\/strong>Kur do t\u00eb p\u00ebrballet Unix me probleme?<\/strong><\/p>\n V\u00ebshtir\u00ebsi t\u00eb ngjashme i presin sistemet Unix jo para vitit 2038, kur datat e ruajtura n\u00eb formatin e p\u00ebrmendur m\u00eb sip\u00ebr do t\u00eb kalojn\u00eb hap\u00ebsir\u00ebn 32-bit. Ka ende 18 vjet, por zhvilluesit e b\u00ebrtham\u00ebs tashm\u00eb po punojn\u00eb p\u00ebr t\u00eb shmangur d\u00ebshtimet e ardhshme.<\/p>\n Problemi i vitit 2038 ndonj\u00ebher\u00eb p\u00ebrmendet si problemi Y2K38. N\u00ebse nuk zgjidhet para t\u00eb mart\u00ebs m\u00eb 19 Janar 2038, pas k\u00ebsaj date sistemet mund t\u00eb mendojn\u00eb se ka ardhur viti 1901. Nj\u00eb nga m\u00ebnyrat p\u00ebr t\u00eb zgjidhur k\u00ebt\u00eb problem \u00ebsht\u00eb kalimi n\u00eb nj\u00eb p\u00ebrfaq\u00ebsim 64-bit t\u00eb informacionit mbi dat\u00ebn dhe or\u00ebn. Disa mendojn\u00eb se kjo do t\u00eb jet\u00eb shum\u00eb m\u00eb e komplikuar se sa duket.<\/p>\n![\"Unix](\"\/wp-content\/uploads\/2020\/01\/aba69e769edb987923b060b6e32f9a00.jpg\")
<\/p>\n![\"Unix](\"\/wp-content\/uploads\/2020\/01\/a720be1bfca58df09540785bf66f556d.jpg\")
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