Menene / dev / null kuma ta yaya zai taimake ku?

Idan har muna da wasu ra'ayoyi game da bishiyar GNU / Linux, aƙalla ya kamata mu saba da / dev / reference, wanda shine ingantaccen inda duk fayilolin da suka shafi na'urorin haɗi. Idan muka duba cikin kundin adireshi / dev / za mu ga "fayil" da ake kira null, amma idan muna so mu bude shi don ganin abin da ke ciki, tsarin zai gaya mana cewa ba zai yiwu ba tunda ba abun ciki bane na yau da kullun. Na sanya kalmar fayil saboda, kamar yadda duk kuka sani don Linux komai (kayan aiki da software) ana wakilta azaman fayil.

Wace na'ura ce / dev / null tayi dace da ita?

Don dalilai masu amfani, yi tunanin kwandon shara, rami mara ƙasa ko sararin samaniya wanda za'a jefa komai ba tare da yiwuwar dawo da shi ba (komai irin wahalar da samarin NASA suka yi).

Amma idan na riga ina da umarni kamar rm, me yasa nake son sabon abu in share?

Saboda yadda dukkan “bakaken ramuka” suke aiki ya banbanta sosai: ta yaya zaku bi diddigin tsarin fitowar kuskure a cikin umarni a cikin rubutun harsashi a lokacin gudu? Anan ne / dev / null ya shigo.

Bari mu ganta da misali.

Mun ƙirƙiri fayil ɗin da ake kira gwaji wanda ke ɗauke da kirtani "Sannu Duniya". Idan muna son wakiltar abun cikin wannan fayil ɗin akan layin umarni, za mu iya yin hakan ta hanyar mai zuwa:

mai amfani @ kwamfutar tafi-da-gidanka: ~ $ gwajin cat
Sannu Duniya

Idan fayil ɗin bai wanzu ba ko kuma aka lasafta shi azaman gwaji (tare da 's' a ƙarshen), za mu sami kuskuren mai zuwa a cikin na'ura mai kwakwalwa:

mai amfani @ kwamfutar tafi-da-gidanka: ~ $ jarabawar cat
cat: gwaje-gwaje: Fayil ko kundin adireshi babu

Me za mu iya yi don kauce wa saƙon kuskure? Da kyau, kawai a tura fitowar umarnin, idan akwai kuskure, zuwa "kwandon shara", wannan shine / dev / null

Ta yaya zamu tantance shi don ya kasance idan akwai kuskure? Anan kuka shigar da daidaitattun shigarwar, fitarwa, da ƙimar kuskure don shirin: STDIN, STDOUT, da STDERR (wanda za'a iya maye gurbin su 0, 1, da 2 bi da bi). Ta wannan hanyar, idan muka sanya ...

mai amfani @ kwamfutar tafi-da-gidanka: ~ $ cat gwaji 2> / dev / null
mai amfani @ kwamfutar tafi-da-gidanka: ~ $

Will Za mu ga cewa ba za a samar da kuskuren sakon a kan na'urar ba.

Dole ne ku yi hankali saboda rubutun yana da mahimmanci: tsakanin haruffa 2 da> bai kamata a sami sarari ba. In ba haka ba, zai ba da masu zuwa:

mai amfani @ kwamfutar tafi-da-gidanka: ~ $ cat gwaji 2> / dev / null
cat: gwaje-gwaje: Fayil ko kundin adireshi babu
cat: 2: Fayil ko kundin adireshi babu

Sabanin haka, sarari tsakanin> da / dev / null ba zai tasiri mummunan sakamakon ba.

Haka nan za mu iya amfani da karkatar da kuskure, misali, don kama kurakurai a cikin fayil ɗin rajista kamar haka:

mai amfani @ kwamfutar tafi-da-gidanka: ~ $ cat gwaji 2> err.log

Wata shari'ar mai ban sha'awa ita ce tarin sakamako a cikin wani fayil ɗin muddin ba a sami kuskure ba, wanda za mu sanya:

mai amfani @ kwamfutar tafi-da-gidanka: ~ $ gwajin cat 1> output_result 2> err.log

A ƙarshe, ya zama dole a sanya kalmar "> / dev / null 2> & 1" wacce a ciki ake hada daidaitaccen fitarwa da kuma fitowar kuskure, ana tura su ta yadda ba yadda za a sami bayanan fitarwa.