Linux CLI

a – pr command for printingpr command is also used to prepare file for printingcommon options: -l length → number of lines per page-number → columns -w width → page width -o offset → left margin offset-f use form feeds -h header → use header instead the filenamels /etc | pr -4 -w 50 |…

a – lpstat commandlpstat command provides information about the status of the printerscommon options: -a → shows accepting state of printers-p → shows all printers -d → shows current default destination-s → shows a status summary -v → shows printers’ attached deviceslpstat -a → shows accepting state of printerslpstat -p → shows all printerslpstat -d…

a – what is a shell scriptshell script is a sequence of commands written in plain text file that is executed by Unix or Linux shellThis script automates the execution of tasks and can be used for a variety of purposesPurpose → helps automate repetitive tasks, making them faster and less error-proneInterpreted language →is interpreted…

a – variablesvariables are used to store and manipulate dataDeclaring variables → by assigning a value to them using =There should be no spaces around =my_variable=”Hello, World!” → declares a variableAccessing variables → using $ with the variable name you can access its valueecho $my_variable → prints the data stored in the variableYou can use…

a – echo in shell scriptsecho command in shell scripting is a fundamental tool for outputting text or variables echo “Hello, World!” → prints Hello Worldecho $greeting → prints the content of $greeting variableyou can use escape characters as wellecho “This is a newline:\nAnd this is a tab:\t.” → using tab escape character-n option avoids…

a – read command in shell scriptsread command is used to accept input from the userIt reads one line from standard input (usually keyboard)Then it assigns it to one or more variablescommon options: -p → displays a custom prompt-n n → read exactly n characters-d “d” → provides a different delimiter-s → silent input (for…

a – functions in shell scriptsFunctions within shell scripts allow you to encapsulate code into reusable blocksIt makes your scripts cleaner and more maintainableDefining a Function → A function in a shell script can be defined using the function keywordor simply by putting parentheses after the function namefunction greet() { } → Method 1: Using…

a – shell functions return codesfunction return codes are used to indicate the success or failure of a function’s execution.also known as exit statusesa return code of 0 indicates successful executionwhile any other value indicates an error or failure.return 0 → returns 0 for successful executionreturn 1 → return 1 for non succesful executioncheck_success $?…

a – flow control in shell scriptsflow control is an essential aspect that allows you to manage the execution of commands…based on certain conditions or loops.It helps in structuring the script to perform different tasks under varying circumstances.Shell scripting supports several flow control constructs, such as if, for, while, and until loops.Key Flow Control Constructs…

a – test command part 1test command is used to evaluate conditional expressionsit returns an exit status based on whether the expression evaluates to true or false.It can be used in if statements, loops, and case statements.test command has a wide range of expressions:file, string and integer expressionsCommon uses:Numeric comparisons: -eq, -ne, -lt, -le, -gt,…