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首页 VMware Workstationv2vgnugzip

VMware Workstationv2vgnugzip.doc

VMware Workstationv2vgnugzip

redman
2018-09-09 0人阅读 举报 0 0 暂无简介

简介:本文档为《VMware Workstationv2vgnugzipdoc》,可适用于IT/计算机领域

GZIP()USERCOMMANDSGZIP()NAMEgzip,gunzip,zcatcompressorexpandfilesSYNOPSISgzipacdfhlLnNqrtvVSsuffixnamegunzipacfhlLnNqrtvVSsuffixnamezcatfhLVnameDESCRIPTIONGzipreducesthesizeofthenamedfilesusingLempelZivcoding(LZ)Wheneverpossible,eachfileisreplacedbyonewiththeextensiongz,whilekeepingthesameownershipmodes,accessandmodificationtimes(ThedefaultextensionisgzforVMS,zforMSDOS,OSFAT,WindowsNTFATandAtari)Ifnofilesarespecified,orifafilenameis"",thestandardinputiscompressedtothestandardoutputGzipwillonlyattempttocompressregularfilesInparticular,itwillignoresymboliclinksIfthecompressedfilenameistoolongforitsfilesystem,gziptruncatesitGzipattemptstotruncateonlythepartsofthefilenamelongerthancharacters(Apartisdelimitedbydots)Ifthenameconsistsofsmallpartsonly,thelongestpartsaretruncatedForexample,iffilenamesarelimitedtocharacters,gzipmsdosexeiscompressedtogzimsdexegzNamesarenottruncatedonsystemswhichdonothavealimitonfilenamelengthBydefault,gzipkeepstheoriginalfilenameandtimestampinthecompressedfileTheseareusedwhendecompressingthefilewiththeNoptionThisisusefulwhenthecompressedfilenamewastruncatedorwhenthetimestampwasnotpreservedafterafiletransferCompressedfilescanberestoredtotheiroriginalformusinggzipdorgunziporzcatIftheoriginalnamesavedinthecompressedfileisnotsuitableforitsfilesystem,anewnameisconstructedfromtheoriginalonetomakeitlegalgunziptakesalistoffilesonitscommandlineandreplaceseachfilewhosenameendswithgz,gz,z,z,zorZandwhichbeginswiththecorrectmagicnumberwithanuncompressedfilewithouttheoriginalextensiongunzipalsorecognizesthespecialextensionstgzandtazasshorthandsfortargzandtarZrespectivelyWhencompressing,gzipusesthetgzextensionifnecessaryinsteadoftruncatingafilewithatarextensiongunzipcancurrentlydecompressfilescreatedbygzip,zip,compress,compressHorpackThedetectionoftheinputformatisautomaticWhenusingthefirsttwoformats,gunzipchecksabitCRCForpack,gunzipcheckstheuncompressedlengthThestandardcompressformatwasnotdesignedtoallowconsistencychecksHowevergunzipissometimesabletodetectabadZfileIfyougetanerrorwhenuncompressingaZfile,donotassumethattheZfileiscorrectsimplybecausethestandarduncompressdoesnotcomplainThisgenerallymeansthatthestandarduncompressdoesnotcheckitsinput,andhappilygeneratesgarbageoutputTheSCOcompressHformat(lzhcompressionmethod)doesnotincludeaCRCbutalsoallowssomeconsistencychecksFilescreatedbyzipcanbeuncompressedbygziponlyiftheyhaveasinglemembercompressedwiththe'deflation'methodThisfeatureisonlyintendedtohelpconversionoftarzipfilestothetargzformatToextractzipfileswithseveralmembers,useunzipinsteadofgunzipzcatisidenticaltogunzipc(Onsomesystems,zcatmaybeinstalledasgzcattopreservetheoriginallinktocompress)zcatuncompresseseitheralistoffilesonthecommandlineoritsstandardinputandwritestheuncompresseddataonstandardoutputzcatwilluncompressfilesthathavethecorrectmagicnumberwhethertheyhaveagzsuffixornotGzipusestheLempelZivalgorithmusedinzipandPKZIPTheamountofcompressionobtaineddependsonthesizeoftheinputandthedistributionofcommonsubstringsTypically,textsuchassourcecodeorEnglishisreducedbyCompressionisgenerallymuchbetterthanthatachievedbyLZW(asusedincompress),Huffmancoding(asusedinpack),oradaptiveHuffmancoding(compact)CompressionspeedwiththefastoptionisroughlyequivalenttothatofcompressCompressionisalwaysperformed,evenifthecompressedfileisslightlylargerthantheoriginalTheworstcaseexpansionisafewbytesforthegzipfileheader,plusbyteseveryKblock,oranexpansionratioofforlargefilesNotethattheactualnumberofuseddiskblocksalmostneverincreasesgzippreservesthemode,ownershipandtimestampsoffileswhencompressingordecompressingOPTIONSaasciiAsciitextmode:convertendoflinesusinglocalconventionsThisoptionissupportedonlyonsomenonUnixsystemsForMSDOS,CRLFisconvertedtoLFwhencompressing,andLFisconvertedtoCRLFwhendecompressingcstdouttostdoutWriteoutputonstandardoutputkeeporiginalfilesunchangedIfthereareseveralinputfiles,theoutputconsistsofasequenceofindependentlycompressedmembersToobtainbettercompression,concatenateallinputfilesbeforecompressingthemddecompressuncompressDecompressfforceForcecompressionordecompressionevenifthefilehasmultiplelinksorthecorrespondingfilealreadyexists,orifthecompresseddataisreadfromorwrittentoaterminalIftheinputdataisnotinaformatrecognizedbygzip,andiftheoptionstdoutisalsogiven,copytheinputdatawithoutchangetothestandardouput:letzcatbehaveascatIffisnotgiven,andwhennotrunninginthebackground,gzippromptstoverifywhetheranexistingfileshouldbeoverwrittenhhelpDisplayahelpscreenandquitllistForeachcompressedfile,listthefollowingfields:compressedsize:sizeofthecompressedfileuncompressedsize:sizeoftheuncompressedfileratio:compressionratio(ifunknown)uncompressedname:nameoftheuncompressedfileTheuncompressedsizeisgivenasforfilesnotingzipformat,suchascompressedZfilesTogettheuncompressedsizeforsuchafile,youcanuse:zcatfileZ|wccIncombinationwiththeverboseoption,thefollowingfieldsarealsodisplayed:method:compressionmethodcrc:thebitCRCoftheuncompresseddatadatetime:timestampfortheuncompressedfileThecompressionmethodscurrentlysupportedaredeflate,compress,lzh(SCOcompressH)andpackThecrcisgivenasffffffffforafilenotingzipformatWithname,theuncompressedname,dateandtimearethosestoredwithinthecompressfileifpresentWithverbose,thesizetotalsandcompressionratioforallfilesisalsodisplayed,unlesssomesizesareunknownWithquiet,thetitleandtotalslinesarenotdisplayedLlicenseDisplaythegziplicenseandquitnnonameWhencompressing,donotsavetheoriginalfilenameandtimestampbydefault(Theoriginalnameisalwayssavedifthenamehadtobetruncated)Whendecompressing,donotrestoretheoriginalfilenameifpresent(removeonlythegzipsuffixfromthecompressedfilename)anddonotrestoretheoriginaltimestampifpresent(copyitfromthecompressedfile)ThisoptionisthedefaultwhendecompressingNnameWhencompressing,alwayssavetheoriginalfilenameandtimestampthisisthedefaultWhendecompressing,restoretheoriginalfilenameandtimestampifpresentThisoptionisusefulonsystemswhichhavealimitonfilenamelengthorwhenthetimestamphasbeenlostafterafiletransferYoucangetthisbehaviorbydefaultbysettingtheGZIPenvironmentvariableasshownintheenvironmentsectionbelowWhendecompressing,thisoptionshouldbeusedwithcarebecauseitmaycreatesecurityproblemsOnUnix,thisoptionisignoredwhengunzipisrunwithrootprivilegesqquietSuppressallwarningsrrecursiveTravelthedirectorystructurerecursivelyIfanyofthefilenamesspecifiedonthecommandlinearedirectories,gzipwilldescendintothedirectoryandcompressallthefilesitfindsthere(ordecompresstheminthecaseofgunzip)SsufsuffixsufUsesuffixsufinsteadofgzAnysuffixcanbegiven,butsuffixesotherthanzandgzshouldbeavoidedtoavoidconfusionwhenfilesaretransferredtoothersystemsAsuffixforcesgunziptotrydecompressiononallgivenfilesregardlessofsuffix,asin:gunzipS""*(**forMSDOS)PreviousversionsofgzipusedthezsuffixThiswaschangedtoavoidaconflictwithpack()ttestTestCheckthecompressedfileintegrityvverboseVerboseDisplaythenameandpercentagereductionforeachfilecompressedordecompressedVversionVersionDisplaytheversionnumberandcompilationoptionsthenquit#fastbestRegulatethespeedofcompressionusingthespecifieddigit#,whereorfastindicatesthefastestcompressionmethod(lesscompression)andorbestindicatestheslowestcompressionmethod(bestcompression)Thedefaultcompressionlevelis(thatis,biasedtowardshighcompressionatexpenseofspeed)ADVANCEDUSAGEMultiplecompressedfilescanbeconcatenated(exceptonVMS,seevmshlp)Inthiscase,gunzipwillextractallmembersatonce,butasasinglefileForexample:gzipcfile>foogzgzipcfile>>foogzThengunzipcfooisequivalenttocatfilefileIncaseofdamagetoonememberofagzfile,othermemberscanstillberecovered(ifthedamagedmemberisremoved)However,youcangetbettercompressionbycompressingallmembersatonce:catfilefile|gzip>foogzcompressesbetterthangzipcfilefile>foogzIfyouwanttorecompressconcatenatedfilestogetbettercompression,do:gzipcdoldgz|gzip>newgzIfacompressedfileconsistsofseveralmembers,theuncompressedsizeandCRCreportedbythelistoptionappliestothelastmemberonlyIfyouneedtheuncompressedsizeforallmembers,youcanuse:gzipcdfilegz|wccIfyouwishtocreateasinglearchivefilewithmultiplememberssothatmemberscanlaterbeextractedindependently,useanarchiversuchastarorzipGNUtarsupportsthezoptiontoinvokegziptransparentlygzipisdesignedasacomplementtotar,notasareplacementENVIRONMENTTheenvironmentvariableGZIPcanholdasetofdefaultoptionsforgzipTheseoptionsareinterpretedfirstandcanbeoverwrittenbyexplicitcommandlineparametersForexample:forsh:GZIP="vname"exportGZIPforcsh:setenvGZIP"vname"forMSDOS:setGZIP=vnameOnVaxVMS,thenameoftheenvironmentvariableisGZIPOPT,toavoidaconflictwiththesymbolsetforinvocationoftheprogramSEEALSOznew(),zcmp(),zmore(),zforce(),gzexe(),zip(),unzip(),compress(),pack(),compact()DIAGNOSTICSExitstatusisnormallyifanerroroccurs,exitstatusisIfawarningoccurs,exitstatusisUsage:gzipcdfhlLnNrtvVSsuffixfileInvalidoptionswerespecifiedonthecommandlinefile:notingzipformatThefilespecifiedtogunziphasnotbeencompressedfile:CorruptinputUsezcattorecoversomedataThecompressedfilehasbeendamagedThedatauptothepointoffailurecanberecoveredusingzcatfile>recoverfile:compressedwithxxbits,canonlyhandleyybitsFilewascompressed(usingLZW)byaprogramthatcoulddealwithmorebitsthanthedecompresscodeonthismachineRecompressthefilewithgzip,whichcompressesbetteranduseslessmemoryfile:alreadyhasgzsuffixnochangeThefileisassumedtobealreadycompressedRenamethefileandtryagainfilealreadyexistsdoyouwishtooverwrite(yorn)Respond"y"ifyouwanttheoutputfiletobereplaced"n"ifnotgunzip:corruptinputASIGSEGVviolationwasdetectedwhichusuallymeansthattheinputfilehasbeencorruptedxxxPercentageoftheinputsavedbycompression(Relevantonlyforvandl)notaregularfileordirectory:ignoredWhentheinputfileisnotaregularfileordirectory,(egasymboliclink,socket,FIFO,devicefile),itisleftunalteredhasxxotherlinks:unchangedTheinputfilehaslinksitisleftunchangedSeeln()formoreinformationUsethefflagtoforcecompressionofmultiplylinkedfilesCAVEATSWhenwritingcompresseddatatoatape,itisgenerallynecessarytopadtheoutputwithzeroesuptoablockboundaryWhenthedataisreadandthewholeblockispassedtogunzipfordecompression,gunzipdetectsthatthereisextratrailinggarbageafterthecompresseddataandemitsawarningbydefaultYouhavetousethequietoptiontosuppressthewarningThisoptioncanbesetintheGZIPenvironmentvariableasin:forsh:GZIP="q"tarxfzblockcomprdevrstforcsh:(setenvGZIPqtarxfzblockcomprdevrst)Intheaboveexample,gzipisinvokedimplicitlybythezoptionofGNUtarMakesurethatthesameblocksize(boptionoftar)isusedforreadingandwritingcompresseddataontapes(ThisexampleassumesyouareusingtheGNUversionoftar)BUGSThelistoptionreportsincorrectsizesiftheyexceedgigabytesThelistoptionreportssizesasandcrcasffffffffifthecompressedfileisonanonseekablemediaInsomerarecases,thebestoptiongivesworsecompressionthanthedefaultcompressionlevel()Onsomehighlyredundantfiles,compresscompressesbetterthangzip

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