everything about linux distro and not only
Killing a process is not a single action. It is a request to the kernel to deliver a signal to a process, and the signal’s meaning is determined by the process itself—unless the signal is SIGKILL, which the kernel enforces without the process’s consent. The LFCS exam places process management under the “Operations Deployment” domain…
Outputting text is the most basic thing a shell script does. You can use echo for simple messages, printf when you need precise formatting, and here documents when you need to pass a block of multi-line text to a command. Key point: echo is quick and convenient but behaves differently across shells. printf is predictable…
Shell scripting is the art of writing a list of commands into a file so the computer can run them for you. Instead of typing the same five commands every morning to back up a folder, you type them once into a script, make it executable, and run it with a single word. That is…
Every process on a Linux system competes for CPU time, and the scheduler decides who gets the processor and for how long. The nice value is the user-space lever for influencing that decision. It is an integer from -20 to 19, where -20 is the highest priority and 19 is the lowest . The name…
56 – shell scripts input text The read command is how a shell script asks the user for input. It reads a line from standard input (usually the keyboard), splits it into fields, and assigns them to variables. With a few options, it can prompt, hide input, read a fixed number of characters, or time…
In the previous chapter, you wrote a Hello World script, made it executable, and passed arguments to it. Those commands were static — the same words, the same paths, every time the script ran. Real scripts are not static. They accept filenames that change, dates that vary, and user input that arrives at runtime. Variables…
A shell session is not limited to running one command at a time. Job control is the mechanism that lets you start a process in the background, suspend a foreground process, resume it later, and list everything the shell is managing. The ampersand (&) starts a command asynchronously, returning the prompt immediately while the process…
Functions let you encapsulate code into reusable blocks. Instead of repeating the same commands in several places, you define them once and call them by name. This makes your scripts cleaner, shorter, and easier to maintain. Key point: Shell functions are not like functions in C or Python. They don’t have a return type, they…
A Proxy wraps an object and intercepts its operations — reads, writes, deletes, function calls, and more. A Reflect object provides the default behaviors that a Proxy can use — the same operations, but with a clean API. Together they’re the foundation of JavaScript metaprogramming. Key point: A Proxy is a trap-based interceptor. It doesn’t…
A script that runs the same commands in the same order every time is useful. A script that makes decisions — that checks whether a file exists before deleting it, whether a service is running before restarting it, whether a user provided the right number of arguments — is powerful. Conditionals are what turn a…