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bashvariables

how bash one line variable affect variable scope

x=1

function f()
{
    echo $x
}

x=2 f #2

function g()
{
    x=3
    a=4
    echo $x
}
a=5
x=2 g  #3
echo $x  #1
echo $a  #4

Why the output is 2 3 1 4 ? Why function f access the one line variable x rather than the global one? Why function g create global variables x and a, but the x does not override outside global one?

Solution

  • Why function f access the one line variable x rather than the global one?

    Because specifying a variable as part of a command sets it in the dynamic scope of the execution of that command (only).

    Why function g create global variables x and a, but the x does not override outside global one?

    g assigns to variables x and a. But in the context of the call x is effectively local to it, on account of a value having been specified for that variable as part of the call. The same is not true of a, so the assignment to it affects the shell environment normally.