Linux CLI

a – extended test command in shell scriptsUnlike the traditional [ ] (or test) which requires spaces around operators, [[ ]] does not have this requirement.It’s generally recommended to use [[ ]] over [ ] for most modern shell scripting needs due to its enhanced functionality and error prevention.Unlike [ ], [[ ]] does not…

a – while loop in shell scriptswhile loop executes its block of commands as long as the given condition remains truesyntaxwhile [ condition ]; do Commands to executedone[ condition ] is evaluated before each iteration. If the condition evaluates to true, the commands inside the loop are executed.Once the commands finish executing, the condition is…

a – case command introductionThe case statement is used for conditional execution based on the value of a variable or expression.It provides a more readable and compact alternative to multiple if-elif-else statements…when you have a limited set of possible values to check against.syntaxcase variable in pattern1) commands if variable matches pattern1 ;; pattern2) commands if…

a – for loop in shell scripts introfor loop is used to iterate over a sequence of items or valuesThis type of loop is very useful for executing the same command or set of commands multiple times with different inputs.syntax: for variable in item1 item2 … itemNdo Commands to be executed for each iterationdonevarialbe is…

a – what is parameter expasion in shell scripts part 1Parameter expansion in a shell script allows you to manipulate variable values in various ways…such as substring extraction, default value assignment, and pattern replacement.common parameter expansions:1. Substring Extraction: ${variable:position} → Extracts the substring from the specified position to the end.${variable:position:length} → Extracts a substring of…

a – Case conversion with parameter expansioncase conversion is converting strings to uppercase or lowercaseIt can be performed using several methods, depending on the shell and the context of the script1. with Parameter Expansion ^^ and ,,Pros:Clean and readable.Fast and efficient.No external commands needed.Cons:Not portable to non-Bash shells (like dash, ksh, or zsh without set…

a – Numbar bases in shell scriptsyou can use variables with different bases by prefixing them with 0x for hexadecimal, 0 for octal, and 0b for binary.*num_hex=0x1A → hexadecimalnum_oct=025 → octalnum_bin=0b1010 → binarywhen dealing with numbers in shell scripts, the shell might not handle leading zeros in variables.025 it might be treated as decimal 25so…

a – unary, assignment and logical operators in shell scriptsShell scripts use various operators to perform operations on variables, strings, numbers, and other data types.Common categories of operators used in shell scripts:Unary, Arithmetic, Relational, Logical, assignment, file test , string and bit operatorsUnary refers to the number of operands, so they take one operand.There are…

a – bc introduction in shell scriptsbc reads input from standard input (stdin) and outputs results to standard output (stdout).You can use it within a shell script by piping expressions to it or by using here documentsWhile basic arithmetic can be done using $((…)) or expr, it is limited to integer operations …and does not…

a – Arrays in shells scripts Part 1arrays are used to store multiple values under a single variable nameArrays are zero-indexed and declared with ()Use quotes to preserve spaces and avoid word splitting.Use ${array[@]} in loops for correct iteration.Associative arrays (with declare -A) allow key-value mapping.Bash does not support native multi-dimensional arrays, but can simulate…