What Is a ShellCommonly Used Command-Line UtilitiesShell ConceptsCommands and PipelinesSubshellsThe pipefail OptionInput and Output RedirectionStreams and File DescriptorsHere-StringHeredocXargsScripting ConceptsExecution PermissionThe ShebangThe Special LC_ALL=C LocaleWriting CommentsStatic Analysis ToolsProfiling Using the Time UtilityBASH Cheat SheetScript Positional ArgumentsVariablesArraysSpecial VariablesTest If a Variable Is SetEmpty, Not Empty, and LengthNumbersIncrement and DecrementMath OperationsRoundingStringsCounting the Number of WordsManipulating String ContentsExtracting a SubstringChecking Matching ContentsReplacing ContentsGlobbingList and SequencesUser InputThe Read CommandThe Select CommandTesting Files and DirectoriesFile ExistenceDirectory ExistenceFlow ControlIf-Elif-ElseCaseControl StructuresFor LoopWhile LoopUntilFunctionsTrapping SignalsSummary