翻译文献-第七章 第八章

外文原文FOREXAMPLE,THISLINEFROM/PROC/TTY/DRIVER/SERIALMIGHTDESCRIBESERIALPORT1WHICHWOULDBECOM2UNDERWINDOWS1UART16550APORT2F8IRQ3BAUD9600TX11RX0THISINDICATESTHATTHESERIALPORTISRUNBYA16550ATYPEUART,USESI/OPORT0X2F8ANDIRQ3FORCOMMUNICATION,ANDRUNSAT9,600BAUDTHESERIALPORTHASSEEN11TRANSMITINTERRUPTSAND0RECEIVEINTERRUPTSSEESECTION64,“HARDWAREDEVICES,”FORINFORMATIONABOUTSERIALDEVICES74KERNELINFORMATIONMANYOFTHEENTRIESIN/PROCPROVIDEACCESSTOINFORMATIONABOUTTHERUNNINGKERNELSCONFIGURATIONANDSTATESOMEOFTHESEENTRIESAREATTHETOPLEVELOF/PROCOTHERSAREUNDER/PROC/SYS/KERNEL741VERSIONINFORMATIONTHEFILE/PROC/VERSIONCONTAINSALONGSTRINGDESCRIBINGTHEKERNELSRELEASENUMBERANDBUILDVERSIONITALSOINCLUDESINFORMATIONABOUTHOWTHEKERNELWASBUILTTHEUSERWHOCOMPILEDIT,THEMACHINEONWHICHITWASCOMPILED,THEDATEITWASCOMPILED,ANDTHECOMPILERRELEASETHATWASUSEDFOREXAMPLECAT/PROC/VERSIONLINUXVERSION221450ROOTPORKYDEVELREDHATCOMGCCVERSIONEGCS2916619990314/LINUXEGCS112RELEASE1TUEMAR7210739EST2000THISINDICATESTHATTHESYSTEMISRUNNINGA2214RELEASEOFTHELINUXKERNEL,WHICHWASCOMPILEDWITHEGCSRELEASE112EGCS,THEEXPERIMENTALGNUCOMPILERSYSTEM,WASAPRECURSORTOTHECURRENTGCCPROJECTTHEMOSTIMPORTANTITEMSINTHISOUTPUT,THEOSNAMEANDKERNELVERSIONANDREVISION,AREAVAILABLEINSEPARATE/PROCENTRIESASWELLTHESEARE/PROC/SYS/KERNEL/OSTYPE,/PROC/SYS/KERNEL/OSRELEASE,AND/PROC/SYS/KERNEL/VERSION,RESPECTIVELYCAT/PROC/SYS/KERNEL/OSTYPELINUXCAT/PROC/SYS/KERNEL/OSRELEASE221450CAT/PROC/SYS/KERNEL/VERSION1TUEMAR7210739EST2000742HOSTNAMEANDDOMAINNAMETHE/PROC/SYS/KERNEL/HOSTNAMEAND/PROC/SYS/KERNEL/DOMAINNAMEENTRIESCONTAINTHECOMPUTERSHOSTNAMEANDDOMAINNAME,RESPECTIVELYTHISINFORMATIONISTHESAMEASTHATRETURNEDBYTHEUNAMESYSTEMCALL,DESCRIBEDINSECTION815THE/PROCFILESYSTEMADVANCEDTOPICSFCNTLANDMMAP743MEMORYUSAGETHE/PROC/MEMINFOENTRYCONTAINSINFORMATIONABOUTTHESYSTEMSMEMORYUSAGEINFORMATIONISPRESENTEDBOTHFORPHYSICALMEMORYANDFORSWAPSPACETHEFIRSTTHREELINESPRESENTMEMORYTOTALS,INBYTESSUBSEQUENTLINESSUMMARIZETHISINFORMATIONINKILOBYTESFOREXAMPLECAT/PROC/MEMINFOTOTALUSEDFREESHAREDBUFFERSCACHEDMEM52969472051961036810084352826122241097728082108416SWAP27139276844003328227389440MEMTOTAL517280KBMEMFREE9848KBMEMSHARED80676KBBUFFERS10720KBCACHED80184KBBIGTOTAL0KBBIGFREE0KBSWAPTOTAL265032KBSWAPFREE222060KBTHISSHOWS512MBPHYSICALMEMORY,OFWHICHABOUT9MBISFREE,AND258MBOFSWAPSPACE,OFWHICH216MBISFREEINTHEROWCORRESPONDINGTOPHYSICALMEMORY,THREEOTHERVALUESAREPRESENTEDTHESHAREDCOLUMNDISPLAYSTOTALSHAREDMEMORYCURRENTLYALLOCATEDOONTHESYSTEMSEESECTION51,“SHAREDMEMORY”THEBUFFERSCOLUMNDISPLAYSTHEMEMORYALLOCATEDBYLINUXFORBLOCKDEVICEBUFFERSTHESEBUFFERSAREUSEDBYDEVICEDRIVERSTOHOLDBLOCKSOFDATABEINGREADFROMANDWRITTENTODISKTHECACHEDCOLUMNDISPLAYSTHEMEMORYALLOCATEDBYLINUXTOTHEPAGECACHETHISMEMORYISUSEDTOCACHEACCESSESTOMAPPEDFILESYOUCANUSETHEFREECOMMANDTODISPLAYTHESAMEMEMORYINFORMATION75DRIVES,MOUNTS,ANDFILESYSTEMSTHE/PROCFILESYSTEMALSOCONTAINSINFORMATIONABOUTTHEDISKDRIVESPRESENTINTHESYSTEMANDTHEFILESYSTEMSMOUNTEDFROMTHEM751FILESYSTEMSTHE/PROC/FILESYSTEMSENTRYDISPLAYSTHEFILESYSTEMTYPESKNOWNTOTHEKERNELNOTETHATTHISLISTISNTVERYUSEFULBECAUSEITISNOTCOMPLETEFILESYSTEMSCANBELOADEDANDUNLOADEDDYNAMICALLYASKERNELMODULESTHECONTENTSOF/PROC/FILESYSTEMSLISTONLYFILESYSTEMTYPESTHATEITHERARESTATICALLYLINKEDINTOTHEKERNELORARECURRENTLYLOADEDOTHERFILESYSTEMTYPESMAYBEAVAILABLEONTHESYSTEMASMODULESBUTMIGHTNOTBELOADEDYET752DRIVESANDPARTITIONSTHE/PROCFILESYSTEMINCLUDESINFORMATIONABOUTDEVICESCONNECTEDTOBOTHIDECONTROLLERSANDSCSICONTROLLERSIFTHESYSTEMINCLUDESTHEMONTYPICALSYSTEMS,THE/PROC/IDESUBDIRECTORYMAYCONTAINEITHERORBOTHOFTWOSUBDIRECTORIES,IDE0ANDIDE1,CORRESPONDINGTOTHEPRIMARYANDSECONDARYIDECONTROLLERSONTHESYSTEM5THESECONTAINFURTHERSUBDIRECTORIESCORRESPONDINGTOPHYSICALDEVICESATTACHEDTOTHECONTROLLERSTHECONTROLLERORDEVICEDIRECTORIESMAYBEABSENTIFLINUXHASNOTRECOGNIZEDANYCONNECTEDDEVICESTHEFULLPATHSCORRESPONDINGTOTHEFOURPOSSIBLEIDEDEVICESARELISTEDINTABLE71SEESECTION64,“HARDWAREDEVICES,”FORMOREINFORMATIONABOUTIDEDEVICENAMESEACHIDEDEVICEDIRECTORYCONTAINSSEVERALENTRIESPROVIDINGACCESSTOIDENTIFICATIONANDCONFIGURATIONINFORMATIONFORTHEDEVICEAFEWOFTHEMOSTUSEFULARELISTEDHEREMODELCONTAINSTHEDEVICESMODELIDENTIFICATIONSTRINGMEDIACONTAINSTHEDEVICESMEDIATYPEPOSSIBLEVALUESAREDISK,CDROM,TAPE,FLOPPY,ANDUNKNOWNCAPACITYCONTAINSTHEDEVICESCAPACITY,IN512BYTEBLOCKSNOTETHATFORCDROMDEVICES,THEVALUEWILLBE2311,NOTTHECAPACITYOFTHEDISKINTHEDRIVENOTETHATTHEVALUEINCAPACITYREPRESENTSTHECAPACITYOFTHEENTIREPHYSICALDISKTHECAPACITYOFFILESYSTEMSCONTAINEDINPARTITIONSOFTHEDISKWILLBESMALLERFOREXAMPLE,THESECOMMANDSSHOWHOWTODETERMINETHEMEDIATYPEANDDEVICEIDENTIFICATIONFORTHEMASTERDEVICEONTHESECONDARYIDECONTROLLERINTHISCASE,ITTURNSOUTTOBEATOSHIBACDROMDRIVECAT/PROC/IDE/IDE1/HDC/MEDIACDROMCAT/PROC/IDE/IDE1/HDC/MODELTOSHIBACDROMXM6702B5IFPROPERLYCONFIGURED,THELINUXKERNELCANSUPPORTADDITIONALIDECONTROLLERSTHESEARENUMBEREDSEQUENTIALLYFROMIDE2IFSCSIDEVICESAREPRESENTINTHESYSTEM,/PROC/SCSI/SCSICONTAINSASUMMARYOFTHEIRIDENTIFICATIONVALUESFOREXAMPLE,THECONTENTSMIGHTLOOKLIKETHISCAT/PROC/SCSI/SCSIATTACHEDDEVICESHOSTSCSI0CHANNEL00ID00LUN00VENDORQUANTUMMODELATLAS_V_9_WLSREV0230TYPEDIRECTACCESSANSISCSIREVISION03HOSTSCSI0CHANNEL00ID04LUN00VENDORQUANTUMMODELQM39100TDSWREVN491TYPEDIRECTACCESSANSISCSIREVISION02THISCOMPUTERCONTAINSONESINGLECHANNELSCSICONTROLLERDESIGNATED“SCSI0”,TOWHICHTWOQUANTUMDISKDRIVESARECONNECTED,WITHSCSIDEVICEIDS0AND4THE/PROC/PARTITIONSENTRYDISPLAYSTHEPARTITIONSOFRECOGNIZEDDISKDEVICESFOREACHPARTITION,THEOUTPUTINCLUDESTHEMAJORANDMINORDEVICENUMBER,THENUMBEROF1024BYTEBLOCKS,ANDTHEDEVICENAMECORRESPONDINGTOTHATPARTITIONTHE/PROC/SYS/DEV/CDROM/INFOENTRYDISPLAYSMISCELLANEOUSINFORMATIONABOUTTHECAPABILITIESOFCDROMDRIVESTHEFIELDSARESELFEXPLANATORYCAT/PROC/SYS/DEV/CDROM/INFOCDROMINFORMATION,IDCDROMC2561999/09/09DRIVENAMEHDCDRIVESPEED48DRIVEOFSLOTS0CANCLOSETRAY1CANOPENTRAY1CANLOCKTRAY1CANCHANGESPEED1CANSELECTDISK0CANREADMULTISESSION1CANREADMCN1REPORTSMEDIACHANGED1CANPLAYAUDIO1753MOUNTSTHE/PROC/MOUNTSFILEPROVIDESASUMMARYOFMOUNTEDFILESYSTEMSEACHLINECORRESPONDSTOASINGLEMOUNTDESCRIPTORANDLISTSTHEMOUNTEDDEVICE,THEMOUNTPOINT,ANDOTHERINFORMATIONNOTETHAT/PROC/MOUNTSCONTAINSTHESAMEINFORMATIONASTHEORDINARYFILE/ETC/MTAB,WHICHISAUTOMATICALLYUPDATEDBYTHEMOUNTCOMMANDTHESEARETHEELEMENTSOFAMOUNTDESCRIPTORTHEFIRSTELEMENTONTHELINEISTHEMOUNTEDDEVICESEECHAPTER6FORSPECIALFILESYSTEMSSUCHASTHE/PROCFILESYSTEM,THISISNONETHESECONDELEMENTISTHEMOUNTPOINT,THEPLACEINTHEROOTFILESYSTEMATWHICHTHEFILESYSTEMCONTENTSAPPEARFORTHEROOTFILESYSTEMITSELF,THEMOUNTPOINTISLISTEDAS/FORSWAPDRIVES,THEMOUNTPOINTISLISTEDASSWAPTHETHIRDELEMENTISTHEFILESYSTEMTYPECURRENTLY,MOSTGNU/LINUXSYSTEMSUSETHEEXT2FILESYSTEMFORDISKDRIVES,BUTDOSORWINDOWSDRIVESMAYBEMOUNTEDWITHOTHERFILESYSTEMTYPES,SUCHASFATORVFATMOSTCDROMSCONTAINANISO9660FILESYSTEMSEETHEMANPAGEFORTHEMOUNTCOMMANDFORALISTOFFILESYSTEMTYPESTHEFOURTHELEMENTLISTSMOUNTFLAGSTHESEAREOPTIONSTHATWERESPECIFIEDWHENTHEMOUNTWASADDEDSEETHEMANPAGEFORTHEMOUNTCOMMANDFORANEXPLANATIONOFFLAGSFORTHEVARIOUSFILESYSTEMTYPESIN/PROC/MOUNTS,THELASTTWOELEMENTSAREALWAYS0ANDHAVENOMEANINGSEETHEMANPAGEFORFSTABFORDETAILSABOUTTHEFORMATOFMOUNTDESCRIPTORS6GNU/LINUXINCLUDESFUNCTIONSTOHELPYOUPARSEMOUNTDESCRIPTORSSEETHEMANPAGEFORTHEGETMNTENTFUNCTIONFORINFORMATIONONUSINGTHESE754LOCKSSECTION83,“FCNTLLOCKSANDOTHERFILEOPERATIONS,”DESCRIBESHOWTOUSETHEFCNTLSYSTEMCALLTOMANIPULATEREADANDWRITELOCKSONFILESTHE/PROC/LOCKSENTRYDESCRIBESALLTHEFILELOCKSCURRENTLYOUTSTANDINGINTHESYSTEMEACHROWINTHEOUTPUTCORRESPONDSTOONELOCKFORLOCKSCREATEDWITHFCNTL,THEFIRSTTWOENTRIESONTHELINEAREPOSIXADVISORYTHETHIRDISWRITEORREAD,DEPENDINGONTHELOCKTYPETHENEXTNUMBERISTHEPROCESSIDOFTHEPROCESSHOLDINGTHELOCKTHEFOLLOWINGTHREENUMBERS,SEPARATEDBYCOLONS,ARETHEMAJORANDMINORDEVICENUMBERSOFTHEDEVICEONWHICHTHEFILERESIDESANDTHEINODENUMBER,WHICHLOCATESTHEFILEINTHEFILESYSTEMTHEREMAINDEROFTHELINELISTSVALUESINTERNALTOTHEKERNELTHATARENOTOFGENERALUTILITYTURNINGTHECONTENTSOF/PROC/LOCKSINTOUSEFULINFORMATIONTAKESSOMEDETECTIVEWORKYOUCANWATCH/PROC/LOCKSINACTION,FORINSTANCE,BYRUNNINGTHEPROGRAMINLISTING82TOCREATEAWRITELOCKONTHEFILE/TMP/TESTFILETOUCH/TMP/TESTFILE/LOCKFILE/TMP/TESTFILEFILE/TMP/TESTFILEOPENING/TMP/TESTFILELOCKINGLOCKEDHITENTERTOUNLOCKINANOTHERWINDOW,LOOKATTHECONTENTSOF/PROC/LOCKSCAT/PROC/LOCKS1POSIXADVISORYWRITE5467080518128802147483647D1B5F74000000000DFEA7D4000000000000000006THE/ETC/FSTABFILELISTSTHESTATICMOUNTCONFIGURATIONOFTHEGNU/LINUXSYSTEMTHEREMAYBEOTHERLINESOFOUTPUT,TOO,CORRESPONDINGTOLOCKSHELDBYOTHERPROGRAMSINTHISCASE,5467ISTHEPROCESSIDOFTHELOCKFILEPROGRAMUSEPSTOFIGUREOUTWHATTHISPROCESSISRUNNINGPS5467PIDTTYSTATTIMECOMMAND5467PTS/28S000/LOCKFILE/TMP/TESTFILETHELOCKEDFILE,/TMP/TESTFILE,RESIDESONTHEDEVICETHATHASMAJORANDMINORDEVICENUMBERS8AND5,RESPECTIVELYTHESENUMBERSHAPPENTOCORRESPONDTO/DEV/SDA5DF/TMPFILESYSTEM1KBLOCKSUSEDAVAILABLEUSEMOUNTEDON/DEV/SDA584597645094292293573663/LSL/DEV/SDA5BRWRW1ROOTDISK8,5MAY51998/DEV/SDA5THEFILE/TMP/TESTFILEITSELFISATINODE181,288ONTHATDEVICELSINODE/TMP/TESTFILE181288/TMP/TESTFILESEESECTION62,“DEVICENUMBERS,”FORMOREINFORMATIONABOUTDEVICENUMBERS76SYSTEMSTATISTICSTWOENTRIESIN/PROCCONTAINUSEFULSYSTEMSTATISTICSTHE/PROC/LOADAVGFILECONTAINSINFORMATIONABOUTTHESYSTEMLOADTHEFIRSTTHREENUMBERSREPRESENTTHENUMBEROFACTIVETASKSONTHESYSTEMPROCESSESTHATAREACTUALLYRUNNINGAVERAGEDOVERTHELAST1,5,AND15MINUTESTHENEXTENTRYSHOWSTHEINSTANTANEOUSCURRENTNUMBEROFRUNNABLETASKSPROCESSESTHATARECURRENTLYSCHEDULEDTORUNRATHERTHANBEINGBLOCKEDINASYSTEMCALLANDTHETOTALNUMBEROFPROCESSESONTHESYSTEMTHEFINALENTRYISTHEPROCESSIDOFTHEPROCESSTHATMOSTRECENTLYRANTHE/PROC/UPTIMEFILECONTAINSTHELENGTHOFTIMESINCETHESYSTEMWASBOOTED,ASWELLASTHEAMOUNTOFTIMESINCETHENTHATTHESYSTEMHASBEENIDLEBOTHAREGIVENASFLOATINGPOINTVALUES,INSECONDSCAT/PROC/UPTIME324893618307233049THEPROGRAMINLISTING77EXTRACTSTHEUPTIMEANDIDLETIMEFROMTHESYSTEMANDDISPLAYSTHEMINFRIENDLYUNITSLISTING77PRINTUPTIMECPRINTTHESYSTEMUPTIMEANDIDLETIMEINCLUDE/SUMMARIZEADURATIONOFTIMETOSTANDARDOUTPUTTIMEISTHEAMOUNTOFTIME,INSECONDS,ANDLABELISASHORTDESCRIPTIVELABEL/VOIDPRINT_TIMECHARLABEL,LONGTIME/CONVERSIONCONSTANTS/CONSTLONGMINUTE60CONSTLONGHOURMINUTE60CONSTLONGDAYHOUR24/PRODUCEOUTPUT/PRINTF“SLDDAYS,LD02LD02LDN”,LABEL,TIME/DAY,TIMEDAY/HOUR,TIMEHOUR/MINUTE,TIMEMINUTEINTMAINFILEFPDOUBLEUPTIME,IDLE_TIME/READTHESYSTEMUPTIMEANDACCUMULATEDIDLETIMEFROM/PROC/UPTIME/FPFOPEN“/PROC/UPTIME”,“R”FSCANFFP,“LFLFN”,FCLOSEFP/SUMMARIZEIT/PRINT_TIME“UPTIME“,LONGUPTIMEPRINT_TIME“IDLETIME”,LONGIDLE_TIMERETURN0THEUPTIMECOMMANDANDTHESYSINFOSYSTEMCALLSEESECTION814,“SYSINFOOBTAININGSYSTEMSTATISTICS”ALSOCANOBTAINTHESYSTEMSUPTIMETHEUPTIMECOMMANDALSODISPLAYSTHELOADAVERAGESFOUNDIN/PROC/LOADAVG8LINUXSYSTEMCALLSSOFAR,WEVEPRESENTEDAVARIETYOFFUNCTIONSTHATYOURPROGRAMCANINVOKETOPERFORMSYSTEMRELATEDFUNCTIONS,SUCHASPARSINGCOMMANDLINEOPTIONS,MANIPULATINGPROCESSES,ANDMAPPINGMEMORYIFYOULOOKUNDERTHEHOOD,YOULLFINDTHATTHESEFUNCTIONSFALLINTOTWOCATEGORIES,BASEDONHOWTHEYAREIMPLEMENTEDALIBRARYFUNCTIONISANORDINARYFUNCTIONTHATRESIDESINALIBRARYEXTERNALTOYOURPROGRAMMOSTOFTHELIBRARYFUNCTIONSWEVEPRESENTEDSOFARAREINTHESTANDARDCLIBRARY,LIBCFOREXAMPLE,GETOPT_LONGANDMKSTEMPAREFUNCTIONSPROVIDEDINTHECLIBRARYACALLTOALIBRARYFUNCTIONISJUSTLIKEANYOTHERFUNCTIONCALLTHEARGUMENTSAREPLACEDINPROCESSORREGISTERSORONTOTHESTACK,ANDEXECUTIONISTRANSFERREDTOTHESTARTOFTHEFUNCTIONSCODE,WHICHTYPICALLYRESIDESINALOADEDSHAREDLIBRARYASYSTEMCALLISIMPLEMENTEDINTHELINUXKERNELWHENAPROGRAMMAKESASYSTEMCALL,THEARGUMENTSAREPACKAGEDUPANDHANDEDTOTHEKERNEL,WHICHTAKESOVEREXECUTIONOFTHEPROGRAMUNTILTHECALLCOMPLETESASYSTEMCALLISNTANORDINARYFUNCTIONCALL,ANDASPECIALPROCEDUREISREQUIREDTOTRANSFERCONTROLTOTHEKERNELHOWEVER,THEGNUCLIBRARYTHEIMPLEMENTATIONOFTHESTANDARDCLIBRARYPROVIDEDWITHGNU/LINUXSYSTEMSWRAPSLINUXSYSTEMCALLSWITHFUNCTIONSSOTHATYOUCANCALLTHEMEASILYLOWLEVELI/OFUNCTIONSSUCHASOPENANDREADAREEXAMPLESOFSYSTEMCALLSONLINUXTHESETOFLINUXSYSTEMCALLSFORMSTHEMOSTBASICINTERFACEBETWEENPROGRAMSANDTHELINUXKERNELEACHCALLPRESENTSABASICOPERATIONORCAPABILITYSOMESYSTEMCALLSAREVERYPOWERFULANDCANEXERTGREATINFLUENCEONTHESYSTEMFORINSTANCE,SOMESYSTEMCALLSENABLEYOUTOSHUTDOWNTHELINUXSYSTEMORTOALLOCATESYSTEMRESOURCESANDPREVENTOTHERUSERSFROMACCESSINGTHEMTHESECALLSHAVETHERESTRICTIONTHATONLYPROCESSESRUNNINGWITHSUPERUSERPRIVILEGEPROGRAMSRUNBYTHEROOTACCOUNTCANINVOKETHEMTHESECALLSFAILIFINVOKEDBYANONSUPERUSERPROCESSNOTETHATALIBRARYFUNCTIONMAYINVOKEONEORMOREOTHERLIBRARYFUNCTIONSORSYSTEMCALLSASPARTOFITSIMPLEMENTATIONLINUXCURRENTLYPROVIDESABOUT200DIFFERENTSYSTEMCALLSALISTINGOFSYSTEMCALLSFORYOURVERSIONOFTHELINUXKERNELISIN/USR/INCLUDE/ASM/UNISTDHSOMEOFTHESEAREFORINTERNALUSEBYTHESYSTEM,ANDOTHERSAREUSEDONLYINIMPLEMENTINGSPECIALIZEDLIBRARYFUNCTIONSINTHISCHAPTER,WELLPRESENTASELECTIONOFSYSTEMCALLSTHATARELIKELYTOBETHEMOSTUSEFULTOAPPLICATIONANDSYSTEMPROGRAMMERSMOSTOFTHESESYSTEMCALLSAREDECLAREDIN81USINGSTRACEBEFOREWESTARTDISCUSSINGSYSTEMCALLS,ITWILLBEUSEFULTOPRESENTACOMMANDWITHWHICHYOUCANLEARNABOUTANDDEBUGSYSTEMCALLSTHESTRACECOMMANDTRACESTHEEXECUTIONOFANOTHERPROGRAM,LISTINGANYSYSTEMCALLSTHEPROGRAMMAKESANDANYSIGNALSITRECEIVESTOWATCHTHESYSTEMCALLSANDSIGNALSINAPROGRAM,SIMPLYINVOKESTRACE,FOLLOWEDBYTHEPROGRAMANDITSCOMMANDLINEARGUMENTSFOREXAMPLE,TOWATCHTHESYSTEMCALLSTHATAREINVOKEDBYTHEHOSTNAME1COMMAND,USETHISCOMMANDSTRACEHOSTNAMETHISPRODUCESACOUPLESCREENSOFOUTPUTEACHLINECORRESPONDSTOASINGLESYSTEMCALLFOREACHCALL,THESYSTEMCALLSNAMEISLISTED,FOLLOWEDBYITSARGUMENTSORABBREVIATEDARGUMENTS,IFTHEYAREVERYLONGANDITSRETURNVALUEWHEREPOSSIBLE,STRACECONVENIENTLYDISPLAYSSYMBOLICNAMESINSTEADOFNUMERICALVALUESFORARGUMENTSANDRETURNVALUES,ANDITDISPLAYSTHEFIELDSOFSTRUCTURESPASSEDBYAPOINTERINTOTHESYSTEMCALLNOTETHATSTRACEDOESNOTSHOWORDINARYFUNCTIONCALLSINTHEOUTPUTFROMSTRACEHOSTNAME,THEFIRSTLINESHOWSTHEEXECVESYSTEMCALLTHATINVOKESTHEHOSTNAMEPROGRAM2EXECVE“/BIN/HOSTNAME”,“HOSTNAME”,/49VARS/01HOSTNAMEINVOKEDWITHOUTANYFLAGSSIMPLYPRINTSOUTTHECOMPUTERSHOSTNAMETOSTANDARDOUTPUT2INLINUX,THEEXECFAMILYOFFUNCTIONSISIMPLEMENTEDVIATHEEXECVESYSTEMCALLTHEFIRSTARGUMENTISTHENAMEOFTHEPROGRAMTORUNTHESECONDISITSARGUMENTLIST,CONSISTINGOFONLYASINGLEELEMENTANDTHETHIRDISITSENVIRONMENTLIST,WHICHSTRACEOMITSFORBREVITYTHENEXT30ORSOLINESAREPARTOFTHEMECHANISMTHATLOADSTHESTANDARDCLIBRARYFROMASHAREDLIBRARYFILETOWARDTHEENDARESYSTEMCALLSTHATACTUALLYHELPDOTHEPROGRAMSWORKTHEUNAMESYSTEMCALLISUSEDTOOBTAINTHESYSTEMSHOSTNAMEFROMTHEKERNEL,UNAMESYS”LINUX”,NODE”MYHOSTNAME”,0OBSERVETHATSTRACEHELPFULLYLABELSTHEFIELDSSYSANDNODEOFTHESTRUCTUREARGUMENTTHISSTRUCTUREISFILLEDINBYTHESYSTEMCALLLINUXSETSTHESYSFIELDTOTHEOPERATINGSYSTEMNAMEANDTHENODEFIELDTOTHESYSTEMSHOSTNAMETHEUNAMECALLISDISCUSSEDFURTHERINSECTION815,“UNAME”FINALLY,THEWRITESYSTEMCALLPRODUCESOUTPUTRECALLTHATFILEDESCRIPTOR1CORRESPONDSTOSTANDARDOUTPUTTHETHIRDARGUMENTISTHENUMBEROFCHARACTERSTOWRITE,ANDTHERETURNVALUEISTHENUMBEROFCHARACTERSTHATWEREACTUALLYWRITTENWRITE1,“MYHOSTNAMEN”,1111THISMAYAPPEARGARBLEDWHENYOURUNSTRACEBECAUSETHEOUTPUTFROMTHEHOSTNAMEPROGRAMITSELFISMIXEDINWITHTHEOUTPUTFROMSTRACEIFTHEPROGRAMYOURETRACINGPRODUCESLOTSOFOUTPUT,ITISSOMETIMESMORECONVENIENTTOREDIRECTTHEOUTPUTFROMSTRACEINTOAFILEUSETHEOPTIONOFILENAMETODOTHISUNDERSTANDINGALLTHEOUTPUTFROMSTRACEREQUIRESDETAILEDFAMILIARITYWITHTHEDESIGNOFTHELINUXKERNELANDEXECUTIONENVIRONMENTMUCHOFTHISISOFLIMITEDINTERESTTOAPPLICATIONPROGRAMMERSHOWEVER,SOMEUNDERSTANDINGISUSEFULFORDEBUGGINGTRICKYPROBLEMSORUNDERSTANDINGHOWOTHERPROGRAMSWORK82ACCESSTESTINGFILEPERMISSIONSTHEACCESSSYSTEMCALLDETERMINESWHETHERTHECALLINGPROCESSHASACCESSPERMISSIONTOAFILEITCANCHECKANYCOMBINATIONOFREAD,WRITE,ANDEXECUTEPERMISSION,ANDITCANALSOCHECKFORAFILESEXISTENCETHEACCESSCALLTAKESTWOARGUMENTSTHEFIRSTISTHEPATHTOTHEFILETOCHECKTHESECONDISABITWISEOROFR_OK,W_OK,ANDX_OK,CORRESPONDINGTOREAD,WRITE,ANDEXECUTEPERMISSIONTHERETURNVALUEIS0IFTHEPROCESSHASALLTHESPECIFIEDPERMISSIONSIFTHEFILEEXISTSBUTTHECALLINGPROCESSDOESNOTHAVETHESPECIFIEDPERMISSIONS,ACCESSRETURNS1ANDSETSERRNOTOEACCESOREROFS,IFWRITEPERMISSIONWASREQUESTEDFORAFILEONAREADONLYFILESYSTEMIFTHESECONDARGUMENTISF_OK,ACCESSSIMPLYCHECKSFORTHEFILESEXISTENCEIFTHEFILEEXISTS,THERETURNVALUEIS0IFNOT,THERETURNVALUEIS1ANDERRNOISSETTOENOENTNOTETHATERRNOMAYINSTEADBESETTOEACCESIFADIRECTORYINTHEFILEPATHISINACCESSIBLE中文翻译例如，这一行从/PROC/TTY/DRIVER/SERIAL也许描述了几个端口1（在WINDOWS平台下也许是COM2）1UART16550APORT2F8IRQ3BAUD9600TX11RX0这指出了几个被A16550ATYPEUART运行的端口，使用I/O接口0X2F8和IRQ3通信，并且运行在9600BRUD上，这些端口被11号或0号中断。详见64节，“硬件设备”，了解更多端口设备信息。74内核信息通过目录/PROC下的许多的目录项可以访问正在运行的内核的配置和状态信息。一些目录项在目录/PROC下的最高层，其它的在/PROC/SYS/KERNEL下741版本信息文件/PROC/VERSION包含一个描述内核发布号和构建版本号的长字符串。它还包含内核被构建的信息编译内核的用户，编译所在机器，编译的日期，所用到的编译器例如CAT/PROC/VERSIONLINUXVERSION221450ROOTPORKYDEVELREDHATCOMGCCVERSIONEGCS2916619990314/LINUXEGCS112RELEASE1TUEMAR7210739EST2000这里指出了系统运行在版本号为2214的内核上，用版本号为112EGCS（EGCS，为实验用GNU编译器系统，为当前GCC项目的前身）。在输出的项目中最重要的部分是，操作系统的名称和内核的版本号和硬件版本，同时分别可以在/PROC目录项中获得。它们分别是/PROC/SYS/KERNEL/OSTYPE，/PROC/SYS/KERNEL/OSRELEASE，和/PROC/SYS/KERNEL/VERSION。CAT/PROC/SYS/KERNEL/OSTYPELINUXCAT/PROC/SYS/DERNEL/OSRELEASE221450CAT/PROC/SYS/KERNEL/VERSION1TUEMAR7210739EST2000742主机名和域名/PROC/SYS/KERNEL/HOSTNAME和/PROC/SYS/KERNEL/DOMAINNAME目录项分别包含计算机的主机名和域名。这与无名的系统调用返回的信息一样，在815节有详述。743内存使用/PROC/MEMINFO目录项包含系统内存使用的信息。展示了物理内存和交换空间的信息。前三行是用比特表示的总内存；后面行代码用千比特概述了信息例如这显示了512MB的物理内存，其中9MB是可使用的，258MB是交换空间，其中216MB是可以使用的。每行对应着物理内存，其他三项的表达。THESHARED列显示了当前系统分配的总共享内存（详见SECTION51，“SHAREDMEMORY”）THEBUFFER列显示了LINUX分配的用于块设备缓冲的的内存。这些缓冲区用于设备驱动保持数据被整块的从硬盘中读和写。THECACHED列显示了LINUX分配给页面高速缓存的内存空间。这块内存用于高速缓存读取映射文件。你可以随便使用命令显示出同样的内存信息。75驱动，挂载，系统文件/PROC文件系统也包含系统中硬盘驱动的信息和系统文件加载他们的信息。751文件系统/PROC/FILESYSTEMS目录项向内核展示了文件系统类型。注意这个列表没有什么用因为它还没有完成文件系统可以被动态的加载和卸载进内核模块。/PROC/FILESYSTEMS列表的内容中仅仅有文件系统的类型那并不能静态的链接在内核或被加载。其他文件系统也许作为系统空闲模块但是还没有被加载。752驱动和分区/PROC文件系统包含设备与IDE控制器及SCSI控制器（如果系统包括它们）连接的信息。在典型的系统中，/PROC/IDE子目录会包含子目录IDE0和IDE1的其中一个或者两个都包含，分别对应系统中的主IDE控制器和副IDE控制器。他们进一步包含子目录对应控制器上的物理设备。控制器或设备目录也许为空如果LINUX还没有识别这些设备的连接。表71中显示了四种可能的IDE设备的完整目录从SECTION64“硬件设备”中可以看出更多IDE设备名字信息。每个IDE设备目录包含几个目录项用于读取确认和配置设备的信息。一些最有用的目录项如下MODEL包含设备模块标识信息的字符串MEDIA包含设备媒体类型。可能的值为DISK，CDROM，TAPE，FLOPPY和UNKNOWN。CAPACITY包含设备的容量，按每块512BYTE计算。注意CDROM设备，取值范围应在1231之间，而不是硬盘驱动的容量。注意容量取值大小代表了整个物理硬盘的容量；系统文件的容量包含分区所用的，所以实际的会小些。例如，这些命令显示了主设备通过副IDE控制器如何确定媒体类型和设备标识的。在这个例子中，结果是一个TOSHIBACDROM驱动。如果系统中存在SCSI设备，/PROC/SCSI/SCSI包含它们标识的值。例如，也许出现这样的结果这台计算机包含一个单信SCSI控制器（被分配在“SCSI