Yuav Sau Li Cas Xaj Asmeskas Hauv Cov Ntawv Npau Suav

Commands, Syntax, thiab Cov Piv txwv

Nrog ib daim ntawv yog-daim ntawv qhia, uas yog hom ntawm cov cai lus pov thawj, koj tuaj yeem ua cov yeeb yam txawv raws li cov sijhawm tau hais tseg. Nws ua kom txoj hauv kev muaj peev xwm txiav txim siab.

Ib qho piv txwv ntawm daim ntawv yooj yim ntawm qhov yog-daim ntawv yuav:

suav = 5 yog [$ count == 5] ces sau "$ count" fi

Hauv qhov ua piv txwv no, qhov sib txawv ntawm "suav" siv los qhia ib yam kev mob uas siv los ua ib feem ntawm qhov yog. Ua ntej cov lus sau tseg, qhov sib txawv ntawm "suav" raug tso tawm qhov "5". Qhov yog-daim ntawv ces mam tshawb xyuas seb qhov value ntawm "suav" yog "5". Yog tias qhov no yog cov lus ntawm nqe lus ntawm lo lus "ces" thiab "fi" raug rhuav tshem, txwv tsis pub muaj cov lus qhia tom qab cov lus sau tseg. Lo lus "lo lus" yog "yog" tig rov qab. Txoj kev sau ntawv bash siv cov rooj sib tham no los cim rau qhov xaus ntawm ib qho kev piav qhia, xws li yog lus los yog rooj plaub-lus.

Cov lus "echo" tau luam tawm nws qhov kev sib cav, qhov no, qhov value ntawm qhov txawv "suav", mus rau qhov chaw davhlau ya nyob twg. Indentation ntawm cov cai ntawm cov ntsiab lus ntawm qhov yog-daim ntawv tuaj yeem pab nyeem tau tiam sis tsis tsim nyog.

Yog tias koj muaj ib qho teeb meem uas muaj ib qho kev cai yuav tsum raug tsuav yog tias qhov kev mob tsis muaj tseeb, koj siv tau lo lus "lwm tus" hauv nqe lus yog, xws li hauv qhov ua piv txwv no:

suav = 5 yog [$ suav == 5] ces sau "$ suav" lwm echo "suav tsis yog 5" qhov

Yog hais tias tus mob "$ count == 5" yog qhov tseeb, lub tshuab luam tawm tus nqi ntawm qhov sib txawv ntawm "suav", txwv tsis pub nws luam cov hlua "suav tsis yog 5".

Yog tias koj xav tau kev sib txawv ntawm ntau cov neeg mob, koj siv tau lo lus "elif", uas yog muab los ntawm "lwm tus yog", xws li hauv qhov ua piv txwv no:

yog [$ count == 5] ces ncha "suav yog tsib" elif [$ count == 6] ces sau "suav yog rau" dua lwm tus ncho "tsis muaj cov saum toj no"

Yog "suav" yog "5", lub tshuab luam tawm "suav yog tsib". Yog tias "suav" tsis yog "5" tab sis "6", lub tshuab luam tawm "suav yog rau xyoo". Yog hais tias nws tsis yog "5" los sis "6", lub kaw lus "tsis muaj leej twg saum toj no".

Raws li koj tau twv tau, koj tuaj yeem muaj ntau qhov "elif" clauses. Ib qho piv txwv nrog ntau yam "elif" yuav tsum:

yog [$ count == 5] ces ncha "suav yog tsib" elif [$ count == 6] ncha "suav yog 6" elif [$ count == 7] ces ncha "suav yog xya" elif [$ count = = 8] ces lo lus "suav yog yim" elif [$ count == 9] ces sau "suav yog cuaj" lwm lo lus "tsis muaj leej twg" saum toj no

Muaj ntau txoj kev sau ntawv zoo li sau nrog cov nqe lus sib txawv ntawm ntau qhov kev sib raug zoo. Nws ua haujlwm zoo sib xws rau qhov yog-cov lus muaj ntau yam "elif" clauses, tiam sis yog qhov xaus. Piv txwv li, cov lus nug saum toj no tuaj yeem rov sau dua nrog nqe lus "case" hauv qab no:

case "$ count" hauv 5) echo "suav yog tsib"; 6) echo "suav yog rau"; 7) echo "suav yog xya"; 8) echo "suav yog yim"; 9) echo "suav yog cuaj"; *) echo "tsis muaj cov saum toj no" esac

Yog tias cov lus-cov lus siv hauv cov kauj vab koog los yog thaum lub sij hawm-xws li hauv qhov ua piv txwv no:

suav = 1 ua tiav = 0 thaum [$ suav-9] pw tsaug zog (suav ++)) yog tias [$ count == 5] ces mus txuas ntxiv "$ count" ua echo Finished

Koj tuaj yeem muaj nested yog cov lus. Simplest nested yog daim ntawv yog ntawm daim ntawv: yog ... ces ... lwm tus ... yog ... ces ... ces ... fi ... fi. Txawm li cas los, if-statement yuav nested nrog arbitrary complexity.

Saib tseem yuav ua li cas kom dhau cov lus sib dhos rau daim ntawv bash , uas qhia tau hais tias yuav ua li cas siv conditionals rau txheej txheem tsis dhau los ntawm kev hais kom ua kab.

Cov tawv nqaij bash kuj muab lwm txoj hauv kev ua yeeb yam, xws li rau-loops , thaum-loops , thiab kab zauv .