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Do while loops have local variables?
One of the important lessons of scope is knowing when it might lead to trouble. In Python, on the other hand, variables declared in if-statements, for-loop blocks, and while-loop blocks are not local variables, and stay in scope outside of the block.
Can you declare a variable in a while loop?
You can put a variable declaration in the test expression of a while loop. What you cannot do is put a declaration statement in other expressions. For instance, in the expression a+b+c, you cannot replace b by int i = f() .
How do you use a variable outside loop?
You have defined the variable outside the loop, so the only thing you need to do is to initialize it, as the error message you should get suggests. String name = “not set”; while(loop) { name = if (condition) // do something to break the loop. } // can use name here.
Can you define a variable in a loop?
It’s not a problem to define a variable within a loop. In fact, it’s good practice, since identifiers should be confined to the smallest possible scope. What’s bad is to assign a variable within a loop if you could just as well assign it once before the loop runs.
What is a local variable and scope of a local variable?
The scope of a variable is the region of a program in which the variable is visible, i.e., in which it is accessible by its name and can be used. Hence, a local variable is visible in the block in which it is declared (including sub-blocks, if present), but is not visible outside that block.
How to ” read ” a variable in Bash while loop?
See §3.6.7 “Here Strings” in the Bash Reference Manual. (I’ve also taken the liberty of adding some double-quotes, and adding -r and IFS= to read, to avoid too much mucking around with the contents of your variables.) while read line ; do echo $line done < < ( code
Can a variable be declared in a while loop?
An automatic variable is local to its block (delimited by {} ), so it cannot be used as a loop counter if declared within the loop body. A2. Your 2. suggestion is the typical way to use a counter in a while loop, although isolating the counter with an outer block is usually not necessary.
Why does a while loop run in a subshell?
In your example the while-loop is executed in a subshell, so changes to the variable inside the while-loop won’t affect the external variable. This is because you’re using the loop with a pipe, which automatically causes it to run in a subshell. Here is an alternative solution using a while loop:
How is a variable modified inside a while loop not remembered?
Each element of a pipeline, even a builtin or shell function, runs in a separate process, a child of the shell running the pipeline. A subprocess cannot affect its parent’s environment. When the read command sets the variable to the input, that variable is set only in the subshell, not the parent shell.