Linux CLI

Converting strings to uppercase or lowercase comes up constantly — normalizing user input, formatting output, comparing values case-insensitively. Bash gives you four different ways to do it, each with different trade-offs in portability, speed, and readability. Key point: The fastest and cleanest method is bash’s built-in parameter expansion (${var^^} and ${var,,}). The most portable is…

Bash arithmetic works in decimal by default, but it can handle octal, hexadecimal, and binary too. Converting between bases is a common task — file permissions, memory addresses, bitmasks, and color codes all use non-decimal bases at some point. Key point: Bash’s arithmetic $((…)) can read numbers in any base using prefixes (0 for octal,…

Shell scripts use operators to perform operations on variables, strings, numbers, and files. They fall into a handful of categories — arithmetic, relational, logical, assignment, file test, string, and bitwise. Knowing which operator to use in which context is half the battle in shell scripting. Key point: The operator you use depends on where you…

Bash arithmetic is integer-only. 10 / 3 gives 3, not 3.33. If you need decimals, square roots, or trigonometric functions, bc is the tool. It’s an arbitrary-precision calculator that reads expressions from stdin and writes results to stdout. Key point: bc is a full calculator language — variables, functions, loops, conditionals. But in shell scripts…

Arrays let you store multiple values under a single variable name. Instead of juggling file1, file2, file3, you have one array files with three elements. Bash arrays are zero-indexed, flexible, and — with associative arrays — can even be keyed by strings. Key point: Bash has indexed arrays (numbered slots) and associative arrays (named keys)….

Linux CLI 1 IntroductionLinux CLI 2 Filesystem NavigationLinux CLI 3 ls, file and less commandsLinux CLI 4 Symbolic and Hard linksLinux CLI 5 WildcardsLinux CLI 6 make directory, copy, move, rename, delete files and directoriesLinux CLI 7 Commands type, whichLinux CLI 8 help, –help and manLinux CLI 9 whatis,apropos and info commandsLinux CLI 10 create…