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[Powered by Google Translate] [Amri-Line Hoja]

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[Christopher Bartholomayo - Chuo Kikuu cha Harvard]

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[Hii ni CS50 - CS50.TV]

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Kipengele muhimu kwa ajili ya mpango huo ni kukubali mtumiaji pembejeo.

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Hivi sasa, tumekuwa Kugundua baadhi ya majukumu ndani ya maktaba CS50

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kukubali mtumiaji pembejeo, kama vile "kupata kamba,"

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ambayo humshauri mtumiaji, wakati maombi ni mbio, kwa kamba.

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>> Hata hivyo, kuna matukio ambapo unataka kutoa programu yako ya pembejeo

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kabla ni kweli mbio.

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Kwa njia hii, huna haja ya kuuliza maelezo ya ziada kutoka kwa mtumiaji yako

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wakati wa utekelezaji kazi rahisi.

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Chukua, kwa mfano, mv au amri ya hoja katika UNIX.

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Amri hii inaruhusu mtumiaji hoja faili kutoka eneo moja hadi jingine.

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Kulingana na kurasa mwongozo, mv anapokea mbili hoja mstari amri:

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faili kwamba inahamishwa na mahali faili inahamishwa kwa.

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Basi mfano hii ina amri kwa hoja mbili.

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Hivyo ni jinsi gani sisi tunasema wetu C mpango wa kutumia hoja hizi amri ya mstari?

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>> Naam, ni zinageuka kuwa kuu, ambayo sisi kutumia katika mipango yote C, ana siri.

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Kuu anapokea vigezo mbili: argc na argv.

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Hebu kwenda juu ya maneno haya.

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>> parameter kwanza, argc, ambayo inasimamia kwa kuhesabu hoja,

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ina aina ya data integer.

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parameter argc ina idadi ya hoja, ikiwa ni pamoja na amri.

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Katika hatua ya amri yetu, ingawa sisi tu kuwa wawili hoja visas,

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thamani argc itakuwa 3.

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parameter pili, argv, ambayo inasimamia kwa vector hoja,

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ni safu ya kuyatumia Char kwamba kumweka kwa masharti.

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>> Hii ina maana kwamba kila kipengele katika argv, kuanzia sifuri,

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ina amri na hoja.

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Kwa mfano, argv [0], ambayo mimi itabidi rejea kama argv sifuri,

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daima vyenye amri kwamba ni kuwa kukimbia -

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katika kesi hiyo, mv.

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argv [1] yana hoja ya kwanza, file.txt,

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na argv [2] yana hoja ya pili, ~ / cs50 /.

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Hoja ya mwisho ya argv daima kuwa null.

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Basi hebu kutekeleza hoja hizi amri-line.

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Katika mazoezi ya awali, sisi kuwekwa utupu, kwa maana ya kitu, kama parameter kuu ya.

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Hata hivyo, ili kwa ajili yetu kwa kutumia hoja amri-line,

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tunahitaji kuondoa batili na mahali ndani ya kuu int argc, char * argv [].

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Sasa, ili kupata kipengele mzima kutoka argv, ambayo ni hoja yako,

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unaweza tu iterate, au kitanzi, kupitia safu kama hii.

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Hivyo, ndani ya mwili kuu, sisi ni kwenda kwenda mbele na aina kwa kitanzi:

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kwa ajili ya (i = 0 int; i <argc; i + +).

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>> Hatuna haja brace curly hapa kwa sababu tuko tu utekelezaji moja mstari wa kanuni

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ndani ya mwili wa kitanzi hii.

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Tutaweza kwenda mbele na hit tab mara moja,

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basi aina ya printf ("argv [% d], kuwakilisha thamani integer,

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ni% s, kwa kamba, basi mwezi line tabia.

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Kisha sisi kutoa printf i kwa iteration ya sasa ya kitanzi

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na argv [i] kwa ajili ya uwakilishi kamba ya hoja ya sasa amri-line.

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Wakati sisi kukimbia kwa hoja mbili, tutaweza kuona hoja kuwa visas katika terminal.

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Mapema sisi alisema kwamba argv uliofanyika safu ya kuyatumia Char.

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>> Hivyo, kama hii ni kesi, ni jinsi gani sisi basi upatikanaji wahusika binafsi katika hoja kila?

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Kwa mfano, ni kama alitaka kuangalia kwa ajili ya tabia maalum katika hoja ya kwanza?

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Naam, jibu ni kwamba tunahitaji kuomba kitanzi nested

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ambayo baadaye iterate kupitia kila kipengele katika string hoja.

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Hii ni jinsi ya kufanya hivyo.

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>> Kwanza, sisi ni kwenda kufanya nakala ya example2.c.

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Kisha, ndani ya kwanza kwa kitanzi,

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sisi ni kwenda kuongeza ziada kwa kitanzi.

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Hivyo kwa (int j = 0, n = strlen (argv [i]),

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ambayo kisha anatupa urefu wa hoja ya sasa,

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; J <n; j + +)

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Sisi ni kwenda magazeti eneo la tabia ya kila

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ndani ya hoja ya sasa kwa kutumia printf.

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Hivyo, printf ("argv [% d], kuwakilisha index ya hoja ya sasa,

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kisha [% d] kwa mara nyingine tena, kuwakilisha tabia ya sasa ya hoja ya sasa,

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ni:% c, kwa ajili ya tabia ya sasa katika hoja.

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Mwisho, sisi kutoa printf na index ya kitanzi nje, i,

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kisha index ya kitanzi ndani.

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>> Na hoja yetu ya mwisho ni tabia halisi printf kutoka hoja zinazotolewa

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katika mstari amri.

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Sasa, kwa sababu mimi kutumika kazi string strlen kupata urefu wa kamba,

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Mimi lazima pia kuongeza maktaba string.h juu ya ni pamoja na wetu.

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Hivyo, kwa kufanya hivyo, tutaweza kwenda juu, na tu chini ya stdio.h, tunakwenda kufanya

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# Pamoja <string.h>.

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>> Hivyo, hebu kukusanya na kukimbia na kutoa hiyo hoja halisi.

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>> Na, kama tunaweza kuona, sasa tuna eneo halisi ya Char kila mtu binafsi katika hoja.

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Hivyo hiyo ni yake. Mimi nina Christopher Bartholomayo, hii ni CS50.

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[CS50.TV]