Shell Programming in Unix, Linux and OS X

Stephen Kochan is the author or co-author of several best-selling titles on Unix and the C language, including Programming in C, Programming in Objective-C, Topics in C Programming, and Exploring the Unix System. He is a former software consultant for AT&T Bell Laboratories, where he developed and taught classes on Unix and C programming.Patrick Wood is the CTO of the New Jersey location of Electronics for Imaging. He was a member of the technical staff at Bell Laboratories when he met Mr. Kochan in 1985. Together they founded Pipeline Associates, Inc., a Unix consulting firm, where he was vice president. They co-authored Exploring the Unix System, Unix System Security, Topics in C Programming, and Unix Shell Programming.

• 1 A Quick Review of the BasicsSome Basic CommandsDisplaying the Date and Time: The date CommandFinding Out Who’s Logged In: The who CommandEchoing Characters: The echo CommandWorking with FilesListing Files: The ls CommandDisplaying the Contents of a File: The cat CommandCounting the Number of Words in a File: The wc CommandCommand OptionsMaking a Copy of a File: The cp CommandRenaming a File: The mv CommandRemoving a File: The rm CommandWorking with DirectoriesThe Home Directory and PathnamesDisplaying Your Working Directory: The pwd CommandChanging Directories: The cd CommandMore on the ls CommandCreating a Directory: The mkdir CommandCopying a File from One Directory to AnotherMoving Files Between DirectoriesLinking Files: The ln CommandRemoving a Directory: The rmdir CommandFilename SubstitutionThe AsteriskMatching Single CharactersFilename NuancesSpaces in FilenamesOther Weird CharactersStandard Input/Output, and I/O RedirectionStandard Input and Standard OutputOutput RedirectionInput RedirectionPipesFiltersStandard ErrorMore on CommandsTyping More Than One Command on a LineSending a Command to the BackgroundThe ps CommandCommand Summary2 What Is the Shell?The Kernel and the UtilitiesThe Login ShellTyping Commands to the ShellThe Shell’s ResponsibilitiesProgram ExecutionVariable and Filename SubstitutionI/O RedirectionHooking up a PipelineEnvironment ControlInterpreted Programming Language3 Tools of the TradeRegular ExpressionsMatching Any Character: The Period (.)Matching the Beginning of the Line: The Caret (^)Matching the End of the Line: The Dollar Sign $Matching a Character Set: The [...] ConstructMatching Zero or More Characters: The Asterisk (*)Matching a Precise Number of Subpatterns: \{...\}Saving Matched Characters: \(...\)cutThe -d and -f OptionspasteThe -d OptionThe -s OptionsedThe -n OptionDeleting LinestrThe -s OptionThe -d OptiongrepRegular Expressions and grepThe -v OptionThe -l OptionThe -n OptionsortThe -u OptionThe -r OptionThe -o OptionThe -n OptionSkipping FieldsThe -t OptionOther OptionsuniqThe -d OptionOther Options4 And Away We GoCommand FilesCommentsVariablesDisplaying the Values of VariablesUndefined Variables Have the Null ValueFilename Substitution and VariablesThe ${variable} ConstructBuilt-in Integer Arithmetic5 Can I Quote You on That?The Single QuoteThe Double QuoteThe BackslashUsing the Backslash for Continuing LinesThe Backslash Inside Double QuotesCommand SubstitutionThe Back QuoteThe $(...) ConstructThe expr Command6 Passing ArgumentsThe $# VariableThe $* VariableA Program to Look Up Someone in the Phone BookA Program to Add Someone to the Phone BookA Program to Remove Someone from the Phone Book${n}The shift Command7 Decisions, DecisionsExit StatusThe $? VariableThe test CommandString OperatorsAn Alternative Format for testInteger OperatorsFile OperatorsThe Logical Negation Operator !The Logical AND Operator -aParenthesesThe Logical OR Operator -oThe else ConstructThe exit CommandA Second Look at the rem ProgramThe elif ConstructYet Another Version of remThe case CommandSpecial Pattern-Matching CharactersThe -x Option for Debugging ProgramsBack to the caseThe Null Command :The && and || Constructs8 'Round and 'Round She GoesThe for CommandThe $@ VariableThe for Without the ListThe while CommandThe until CommandMore on LoopsBreaking Out of a LoopSkipping the Remaining Commands in a LoopExecuting a Loop in the BackgroundI/O Redirection on a LoopPiping Data into and out of a LoopTyping a Loop on One LineThe getopts Command9 Reading and Printing DataThe read CommandA Program to Copy FilesSpecial echo Escape CharactersAn Improved Version of mycpA Final Version of mycpA Menu-Driven Phone ProgramThe $$ Variable and Temporary FilesThe Exit Status from readThe printf Command10 Your EnvironmentLocal VariablesSubshellsExported Variablesexport -pPS1 and PS2HOMEPATHYour Current DirectoryCDPATHMore on SubshellsThe .CommandThe exec CommandThe (...) and { ...; } ConstructsAnother Way to Pass Variables to a SubshellYour .profile FileThe TERM VariableThe TZ Variable11 More on ParametersParameter Substitution${parameter}${parameter:-value}${parameter:=value}${parameter:?value}${parameter:+value}Pattern Matching Constructs${#variable}The $0 VariableThe set CommandThe -x Optionset with No ArgumentsUsing set to Reassign Positional ParametersThe -- OptionOther Options to setThe IFS VariableThe readonly CommandThe unset Command12 Loose EndsThe eval CommandThe wait CommandThe $! VariableThe trap Commandtrap with No ArgumentsIgnoring SignalsResetting TrapsMore on I/O<&- and >&-In-line Input RedirectionShell ArchivesFunctionsRemoving a Function DefinitionThe return CommandThe type Command13 Rolo RevisitedData Formatting ConsiderationsroloaddludisplayremchangelistallSample Output14 Interactive and Nonstandard Shell FeaturesGetting the Right ShellThe ENV FileCommand-Line EditingCommand HistoryThe vi Line Edit ModeAccessing Commands from Your HistoryThe emacs Line Edit ModeAccessing Commands from Your HistoryOther Ways to Access Your HistoryThe history CommandThe fc CommandThe r CommandFunctionsLocal VariablesAutomatically Loaded FunctionsInteger ArithmeticInteger TypesNumbers in Different BasesThe alias CommandRemoving AliasesArraysJob ControlStopped Jobs and the fg and bg CommandsMiscellaneous FeaturesOther Features of the cd CommandTilde SubstitutionOrder of SearchCompatibility SummaryAppendixes A Shell SummaryB For More Information