Bash Scripting: Everything you need to know about Bash

Bash ScriptingEverything you need to know about BashWhat’s a shell, and why should you care about it?Any recent computer operating system (byrecent, we mean since about 1970) hassome sort of user interface—some way of specifying commands for the operating sys-tem to execute. But in lots of operating systems, that command interface was reallybuilt in and there was only one way to talk to the computer. Furthermore, an operat-ing system’s command interface would let you execute commands, but that wasabout all. After all, what else was there to do?The Unix operating system popularized the notion of separating the shell(the part ofthe system that lets you type commands) from everything else: the input/output sys-tem, the scheduler, memory management, and all of the other things the operating system takes care of for you (and that most users don’t want to care about). The shell was just one more program; it was a program whose job was executing other pro-grams on behalf of users.But that was the beginning of a revolution. The shell was just another program thatran on Unix, if you didn’t like the standard one, you could create your own. So bythe end of Unix’s first decade, there were at least two competing shells: the Bourne Shell,sh(which was a descendant of the original Thomson shell), plus the C Shell,csh. By the end of Unix’s second decade, there were a few more alternatives: theKorn shell, (ksh), and the first versions of the bash shell (bash).IntroductionWhat is shell propmt?When does paralysis begin and end?CommandsSimple commandsComplex commandsCompound commandsWhat is shell script?The advantages are found only in bashWhat is interactive chance?Chapter OneCreate and run the Bash programWriting and namingIn which coincidence will the program work?Add commentsChapter IIBash environmentShell initialization filesVariables in BashTypes of variablesClassify variables based on their contentCreate variablesExport variablesThe difference between * $ and @ $Recycle shell programs using variablesQuote characters in BashUtility quote typefacesCharacter escapeSingle quotation marksDouble quotation marksLocalesExpansions in BashExpanded swastika {}Length Expansion (~)Substitution of commandsComputational expansionProcess substitutionExpands file namesAlternative commands in BashUtility alternative commandsCreate and delete alternate commandsFaster functionsChapter IIIStereotypes in BashRegular ExpressionsThe difference between basic and extended stereotypesGrep commandGrep command and typical expressionsAxes of lines and wordsCharacter TypesWildcardsMatch patterns using Bash featuresCharacter RangesChapter IVConditional structures in BashExpressions used with ifThe commands that follow are thenScan filesCheck the chance optionsSimple applications on the if statementText comparisonsIf / then / else is builtThe difference between [] and [[]]Examine the command line argumentsThe names of files that contain spacesNested if statementsLogical operationsUse the exit statement with ifChapter VRepetitive tasks in BashEpisode for in BashHow to make a loop for iterativeExamplesBasename commandWhile loop in BashHow to make a while loopWhile nested loopsCalculate the averageUntil loop in BashHow to make a loop untilThe Break and Continue commandsBreak commandContinue commandChapter VIFunctions in BashWhat are functions?Functions SyntaxPosition coefficients in functionsDisplaying FunctionsRecyclingAdjust the pathunset pathmungeChapter VIIWriting interactive Bash programsView user messages in BashInteractive or non-interactive programs?Use the echo commandGet user input in BashUse the read commandRequest user inputRedirection and file descriptorsRedirect errors