What is the purpose of “&&” in a shell command?
As far as I know, using & after the command is for running it in the background. Example of & usage: tar -czf file.tar.gz dirname & But how about &&? (example)
syntax
What is the Java ?: operator called and what does it do?
Yes, it is a shorthand form of It’s called the conditional operator. Many people (erroneously) call it the ternary operator, because it’s the only ternary (three-argument) operator in Java, C, C++, and probably many other languages. But theoretically there could be another ternary operator, whereas there can only be one conditional operator. The official name is given in the Java Language … Read more
Nested JSON objects – do I have to use arrays for everything?
You don’t need to use arrays. JSON values can be arrays, objects, or primitives (numbers or strings). You can write JSON like this: You can use it like this:
What do << or >>> in java mean?
They are Bitwise Bit shift operators, they operate by shifting the number of bits being specified . Here is tutorial on how to use them. The signed left shift operator “<<” shifts a bit pattern to the left The signed right shift operator “>>” shifts a bit pattern to the right. The unsigned right shift operator “>>>” … Read more
What does “-ne” mean in bash?
This is one of those things that can be difficult to search for if you don’t already know where to look. [ is actually a command, not part of the bash shell syntax as you might expect. It happens to be a Bash built-in command, so it’s documented in the Bash manual. There’s also an external … Read more
Are multi-line strings allowed in JSON?
JSON does not allow real line-breaks. You need to replace all the line breaks with \n. eg: “first line second line” can saved with: “first line\nsecond line” Note: for Python, this should be written as: “first line\\nsecond line” where \\ is for escaping the backslash, otherwise python will treat \n as the control character “new line”
Python: SyntaxError: keyword can’t be an expression
sum.up is not a valid keyword argument name. Keyword arguments must be valid identifiers. You should look in the documentation of the library you are using how this argument really is called – maybe sum_up?
Are multi-line strings allowed in JSON?
Is it possible to have multi-line strings in JSON? It’s mostly for visual comfort so I suppose I can just turn word wrap on in my editor, but I’m just kinda curious. I’m writing some data files in JSON format and would like to have some really long string values split over multiple lines. Using … Read more
What is the difference between syntax and semantics in programming languages?
TL; DR In summary, syntax is the concept that concerns itself only whether or not the sentence is valid for the grammar of the language. Semantics is about whether or not the sentence has a valid meaning. Long answer: Syntax is about the structure or the grammar of the language. It answers the question: how do I … Read more
The difference between += and =+
a += b is short-hand for a = a + b (though note that the expression a will only be evaluated once.) a =+ b is a = (+b), i.e. assigning the unary + of b to a. Examples: