Question

I want to construct a complicate variable, let’s see :

set entry_arg [lindex $argv 1]
set command_to_launch {extrernal_command_tool -option "set var $entry_arg" -other_option}
exec $command_to_lauch

The command is launched, no problem …

but, the problem is that the tool get $entry_arg and crash … This is due to the ” ” that don’t allow tcl to interpret de variable

set command_to_launch {extrernal_command_tool -option "set var [lindex $argv 1]"  -other_option}

Have the same problem !

How can I solve it ?

Answer 1

The problem isn’t "", it’s {}. Try:

set entry_arg [lindex $argv 0]
set command_to_launch "extrernal_command_tool -option $entry_arg -other_option"
set output [eval exec $command_to_lauch]

You need to learn about interpolation, quoting and braces, like this: Understanding the usage of braces

(Also, I suspect you want to use [lindex $argv 0] — TCL uses the variable argv0 as the program name, and the arguments start at index 0, unlike C and other languages.)

Edit:
You might actually mean this, if you really want a quoted argument like "set var xxx":

    set command_to_launch "extrernal_command_tool -option \"set var $entry_arg\" -other_option"