操作系统原理与设计第10章FSinterface（文件系统概述）陈香兰中国科学技术大学计算机学院2009年12月......提纲FileConceptAccessMethodsDirectoryStructureFileSystemMountingProtection小结和作业......FileSystem......OutlineFileConceptAccessMethodsDirectoryStructureFileSystemMountingProtection小结和作业......FileConceptIOSprovidesauniformlogicalviewofinfomationstoragedespitethevariousstoragemedia.IAfileisalogicalstorageunit.IAfileisanamedcollectionofrelatedinformationthatisrecordedonsecondarystorage.ITypes:IData:numeric;character;binaryIProgramIIngeneral,afileisasequenceofbits,bytes,lines,orrecords.Ithemeaningisdefinedbythefile’screatoranduser.IContiguouslogicaladdressspace......File.AttributesIName–onlyinformationkeptinhuman-readableformIAnameisusuallyastringofcharacters,suchasexample.cIuppercasevs.lowercase;careornotcareIIdentifier–uniquetag(number)identifiesfilewithinFSIitisthenon-human-readablenameforthefileIType–neededforsystemsthatsupportdifferenttypesILocation–pointertofilelocationondeviceISize–currentfilesize;mayalsoincludeMAXsizeIProtection–Access-controlinformation:whocandoreading,writing,executingITime,date,anduseridentification–dataforprotection,security,andusagemonitoringIInformationaboutfilesarekeptinthedirectorystructure,whichismaintainedonthedisk.......FileOperationsIIFileisanabstractdatatype.OSprovidesthe6basicsystemcalls1.Create:allocatespace+createandirectoryentry2.Write:writepointer3.Read:readpointer4.Repositionwithinfile:alsoknownasseek5.Delete:releasespace+erasethedirectoryentry6.Truncate:filelen=0;releasespace;allotherattributesremainunchangedIothers:Iforfile:append,renameIforfileattribute:chown,chmod,:::Ifordirectory&directoryentries:IOpen(Fi)–searchthedirectorystructureondiskforentryFi,andmovethecontentofentrytomemoryIClose(Fi)–movethecontentofentryFiinmemorytodirectorystructureondisk......OpenFiles&Open-FileTableIIOpen-filetable:asmalltablecontaininginformationaboutallopenfilesISeveralprocessesmayopenth