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Variable Scope in Shell and Oil

NOTE: Most important content has been moved to the variables doc.

This doc has details for advanced users.

Details

Three Semantics for Cell Lookup

Cells are locations for variables.

Named after enums.

scope_e.Dynamic

What shell uses

• setref: Dynamic with nameref (no shopt)
  • Built on bash's nameref feature: declare -n.
  • i.e. "Out Params"
  • Does not respect `shopt.

scope_e.LocalOrGlobal

In Oil, it does one of three things:

1. mutates an existing local
2. mutates an existing global
3. create a new global

In shell, it does these things:

2. Mutate any variable of th e name up the stack.

scope_e.LocalOnly

For loop variables, etc. Mutates exactly one scope!

Where Are These Semantics Used?

LocalOrGlobal For Reading Variables, and for setvar

• reading global vars is normal

Constructs That Retrieve Cells:

The other ones deal with values. These deal with cells.

• GetCell() and GetAllCells()
  • declare -p to print variables
  • ${x@a} to print flags
  • pp .cell
  • weird TZ test in printf. I think this could just look in the environment itself? Do getenv()?
    • yeah I think this is a separate case
    • I think it should just look for a GLOBAL honestly

Related Links

• Oil Variables