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tcleval

Accessing a value in dynamically named array

I need to access a value in array which has been created in a dynamic way - meaning array's name is stored in a variable. To do this I try to use eval command but then get lost with the usage of $. I do succeed to retrieve a key-value pair because no $ is required in a command like array get but what I need to use is array(key) pattern.

The expected simplified code would look like:

set arr foo;
set val1 v1;
set val2 v2;

eval "array set $arr \{
key1 $val1
key2 $val2
\}";

eval "set x \${$arr(key1)}";

As for the last line which is actually the failure, I've tried the following options:

eval "set x \${$arr}(key1)";

or

eval "set x \$$arr(key1)"

and even more weird but with no success.

Solution

  • Remember that $var is shorthand for [set var]. So you could write the command as:

    set x [set ${arr}(key1)]

    But for these kind of situations, it's probably easiest to use upvar:

    upvar 0 $arr arrvar
set x $arrvar(key1)

    The upvar command creates an alias to a variable in the specified stack frame. By specifying the level as '0', it creates an alias to another variable in the current scope. So this command makes arrvar an alias for the variable name stored in the arr variable.