TCL: get single variable to be interpreted as multiple arguments

Question

How can I get a single string variable with spaces in it in TCL to be interpreted as multiple arguments? I can't change the proc definition.

Here is an example of what I mean:

set my_options ""
if { "$some_condition" == 1 } {
    append my_options " -optionA"
}
if { "$some_other_condition" == 1 } {
    append my_options " -optionB"
}
set my_options [string trim $my_options]
not_my_proc ${my_options} ;# my_options gets interpreted as a single arg here and causes a problem:
# Flag '-optionA -optionB' is not supported by this command.

glenn jackman · Accepted Answer · 2019-06-13 15:14:46Z

1

This is where you use the argument expansion syntax:

not_my_proc {*}$my_options
# ..........^^^

Although I'd recommend using a list instead of a string:

if for some reason the my_options string is not a well-formed list, you'll see an error thrown
if any of the options takes a space, a list is the proper data structure:

set my_options [list]
lappend my_options {-option1}
lappend my_options {-option2 "with a parameter"}
not_my_proc {*}$my_options

answered Jun 13, 2019 at 15:14

glenn jackman

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1 Comment

PistoletPierre Over a year ago

Ohh fabulous - I knew there had to be a way! Thanks Glenn!

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