To search through the man pages for some keywords, use the -k option. man -k [keyword] This shows a result of the commands, and routines that match the keyword with a one-line description of what they are about. man -k passwd shows all the possible entries for passwd in the manual pages. The apropos The man -k [keyword] command is similar to a help utility called apropos which is available both on Unix and Linux. See it as a shortcut. ...

There are many ways to get help as a Linux administrator, manual pages are one of them as they are always close - accessible via the terminal. The manual pages, called “man pages” is a local documentation and description of software packages, drivers, routines, and libraries on a Linux machine. To use it run man [command|library|routine|driver] and replace the command with the name of a command to find a manual. ...

Communication between service workers and the clients browser window can be achieved by simply doing: 1 2 3 self.clients.matchAll().then((clients) => { clients.forEach((client) => client.postMessage({ msg: "Hello from SW" })) }) The variable self is a reserved keyword in a service worker context. It references the global scope of the current worker execution scope and has some useful properties. It is like the window object of a JavaScript browser context. In the above snippet, all the clients that run the service worker are loaded, then the .postMessage is called to send message directly to the original javascript runtime of the service worker. ...

First, install CompileDaemon: 1 $ go get github.com/githubnemo/CompileDaemon && go install github.com/githubnemo/CompileDaemon Then, from the root of the project, create a Make file: 1 $ touch Makefile And add the below content: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 GOCMD ?= go GOBUILD = $(GOCMD) build GOCLEAN = $(GOCMD) clean GOTEST = $(GOCMD) test GOGET = $(GOCMD) get BINARY_NAME = project_name BINARY_UNIX = $(BINARY_NAME)_unix default: all all: test build build: $(GOBUILD) -o ../$(BINARY_NAME) -v -ldflags="-X main.VERSION=$(TAG)" test: $(GOTEST) -v ./... clean: $(GOCLEAN) rm -f $(BINARY_NAME) rm -f $(BINARY_UNIX) run: build ./$(BINARY_NAME) dev: CompileDaemon -build="$(GOBUILD) -o ../$(BINARY_NAME)" -command="../$(BINARY_NAME)" -color="true" -exclude-dir=.git -exclude=".#*" Finally, from the root of your project: ...

When programming Erlang, you should think like you are writing an English essay. In Erlang, functions are not very different to what a traditional programming language offers, but they are written very differently in Erlang. To declare a function in the Erlang Repl, you will have to use the fun keyword. 1 Name = fun(X) -> X. The above code will store the the declaration of a function called Name and would receive an argument called X. ...

If you come from a conventional programming language background, the way Erlang handles assignment is expected to look wonky, but it is not. There is nothing like an assignment in Erlang programming language; there is a different approach to accessing values in memory, which is the pattern-matching operations. With Java, PHP, Python, C, C++, and likes, the = symbol implies take the values from the right, and store it into the memory, then give me the reference of the location in memory and store it in the expression at the left. ...

If you have worked with other languages like JavaScript, Java, Python etc, you would be surprised by what Erlang understands as variable. In Erlang, variables starts with uppercase letter, thus, C, X, Ape, Ant are all valid identifiers for Erlang variables. Variables can not start with lowercase letter or begin with a number. Erlang variables can include can alphanumeric characters, an underscore and @ symbol. 1 2 3 X = 1. %% Valid y = 2. %% Invalid 1X = 2. %% Invalid When assigning to a variable - as we do call it in other languages, Erlang actually does something called pattern matching. Comparing the values on the right to the values on the left. ...

Without JavaScript, dynamic UI is possible with just CSS action class selectors. Case study Help text for input element which is only visible when the input is focused. The HTML 1 2 3 4 <div class="input-cont"> <input type="text" placeholder="Focus me" autofocus /> <span class="help" data-help="Enter your email"></span> </div> To achieve the above, a span holding the help text in a data-help attribute as a sibling to the actual input. Both the input and the span are children to a parent div with class name input-cont. ...

If you have used WhatsApp or Facebook Chat, then you have one way or the other interacted with an Erlang-backed system. Erlang is a language created for the telecommunication industry by Jor Armstrong, Robert Virding, and Mike Williams in 1986. It was recorded that Jor Armstrong claimed he was provided a library and did not know what to do with it, then they taught him to solve the reliability and concurrent problem of the telecommunication industry, and that gave birth to Erlang. ...

CSS can keep count of numbers without writing any additional JavaScript. It does this by taking note the amount of time a CSS block affects a page then incrementing the counter for that block if the counter-increment rule is implemented. For example: 1 2 3 input:invalid { counter-increment: invalid-count; } With no JavaScript at all, CSS understands that whenever there is an invalid element, it should increment the count for the invalid-count identifier. ...