Iingcamango ezingezizo zabaProgram malunga nexesha le-Unix

Ndiyaxolisa UPatrick McKenzie.

Izolo UDanny Ndibuze malunga neenyani ezinomdla malunga nexesha le-Unix, kwaye ndakhumbula ukuba ngamanye amaxesha isebenza ngokungafaniyo ngokupheleleyo.

Ezi zibakala zintathu zibonakala zisengqiqweni kwaye zisengqiqweni, akunjalo?

1. Ixesha le-unix linani lemizuzwana ukususela nge-1 kaJanuwari 1970 00:00:00 UTC.
2. Ukuba ulinda kanye umzuzwana omnye, ixesha le Unix liza kutshintsha kanye ngomzuzwana omnye.
3. Ixesha le-unix alize libuye umva.

Akukho nanye kwezi iyinyani.

Kodwa akwanelanga ukuthi nje, “Akukho nanye kwezi iyinyani,” ngaphandle kokucacisa. kutheni. Jonga ngezantsi ukuze ufumane iingcaciso. Kodwa ukuba ufuna ukuzicingela, musa ukuskrola udlule umfanekiso wewotshi!

Iwotshi yetheyibhile ukusuka kwi-1770s. Ihlanganiswe nguJohn Leroux. Ukusuka Wamkelekile ingqokelela. Ipapashwe phantsi kwelayisensi CC BY

Zontathu ezi mbono ziphosakeleyo zinesizathu esinye: xhuma imizuzwana. Ukuba awuqhelananga nemizuzwana yokuxhuma, nantsi ireferensi ekhawulezayo:

Ixesha le-UTC limiselwa yimiba emibini:

• Ixesha leAtom yeHlabathi: I-avareji yokufunda kumakhulu ewotshi zeathom kwihlabathi jikelele. Sinokulinganisa okwesibini ngeempawu zombane zeathom, yaye lo ngowona mlinganiselo uchanekileyo wexesha owaziwa yinzululwazi.
• Ixesha leHlabathi, ngokusekwe ekujikelezeni koMhlaba ujikeleze i-axis yawo. Uvukelo olunye olupheleleyo lusuku olunye.

Ingxaki kukuba la manani mabini awasoloko edibana. Ukujikeleza koMhlaba akuhambelani - ngokuthe ngcembe kuyehla, ngoko ke iintsuku zeXesha leHlabathi ziba nde. Kwelinye icala, iiwotshi zeathom zichanekile ngendlela yobutyholi yaye aziguquguquki kwizigidi zeminyaka.

Xa amaxesha amabini ephuma kwi-sync, isibini siyongezwa okanye sisuswe kwi-UTC ukuze sibabuyisele kungqamaniso. Ukususela ngo-1972 inkonzo IERS (eqhuba le meko) yongeze imizuzwana engama-27 eyongezelelweyo. Isiphumo saba yi-27 yeentsuku ze-UTC kunye nexesha le-86 imizuzwana. Ngokwethiyori, usuku olunobude bemizuzwana engama-401 (kuthatyathwe enye) lunokwenzeka. Zombini iinketho ziyaphikisana nengqikelelo esisiseko yexesha le-Unix.

Ixesha le-Unix lithatha ukuba usuku ngalunye luthatha imizuzwana eyi-86 (400 × 60 × 60 = 24), ngaphandle kwemizuzwana eyongezelelweyo. Ukuba ukutsiba okunjalo kwenzeka, ngoko ixesha le-Unix litsiba umzuzwana omnye, okanye libale imizuzwana emibini kwenye. Ukusukela ngo-86, ilahlekile imizuzwana engama-400 yokutsiba.

Ngoko ke iimbono zethu eziphosakeleyo kufuneka zongezwe ngolu hlobo lulandelayo:

• Ixesha le-unix linani lemizuzwana ukusukela nge-1 kaJanuwari 1970 00:00:00 UTC thabatha imizuzwana yokutsiba.
• Ukuba ulinda kanye umzuzwana omnye, ixesha le-Unix liza kutshintsha kanye ngomzuzwana omnye, ngaphandle kokuba i-leap yesibini isusiwe.

  Kuze kube ngoku, imizuzwana ayizange isuswe ekusebenzeni (kwaye ukucotha kokujikeleza koMhlaba kuthetha ukuba oku akunakwenzeka), kodwa ukuba kwenzeka, kuya kuthetha ukuba usuku lwe-UTC luya kuba lufutshane lwesibini. Kule meko, isibini sokugqibela se-UTC (23:59:59) siyalahlwa.

  Usuku ngalunye lwe-Unix lunenani elifanayo lemizuzwana, ngoko ke i-Unix yokugqibela yosuku olufutshane aluyi kuhambelana naliphi na ixesha le-UTC. Nantsi indlela ekhangeleka ngayo, kwisithuba sekota-yesibini:

  
  
  Ukuba uqala ngo-23:59:58:00 UTC kwaye ulinde umzuzwana omnye, ixesha le-Unix liya kuqhubela phambili imizuzwana emibini ye-UTC kwaye i-Unix 101 timestamp ayiyi kwabelwa nabani na.

• Ixesha le-unix alinakuze libuyele umva, kude kongezwe umzuzwana wokutsiba.

  Oku sele kwenzekile amaxesha angama-27 ekusebenzeni. Ekupheleni kosuku lwe-UTC, isibini esongezelelweyo songezwa kwi-23: 59: 60. I-Unix inenani elifanayo lemizuzwana ngosuku, ngoko ayinako ukongeza isibini esongezelelweyo- endaweni yoko kufuneka iphinde izitampu ze-Unix kwisekondi yokugqibela. Nantsi indlela ekhangeleka ngayo, kwisithuba sekota-yesibini:

  
  
  Ukuba uqala ngo-23:59:60.50 kwaye ulinde isiqingatha sesibini, ixesha le-Unix ubuya ngesiqingatha sesibini, kunye ne-Unix 101 isitampu sexesha sihambelana nesekondi ezimbini ze-UTC.

Ezi mhlawumbi ayizizo kuphela ezingaqhelekanga zamaxesha e-Unix - kanye into endiyikhumbule izolo.

Ixesha - kakhulu into engaqhelekanga.

umthombo: www.habr.com