CODEWITHSUNDEEP
tclproc
bharath kumar
bharath kumar

Reputation: 165

using variables assingned in the script inside the proc in TCL

i want to use the variable assigned outside (proc) to be used inside the proc . For example i tried the following thing

set a 10
proc myproc { } {
puts $a
}
myproc

I am expecting the above script to print 10 . But the above script is erroring out "can't read "a": no such variable"

I cannot pass $a as argument to script because i have lot such variables i want to use inside my proc inside my script . Could you please help me to solve this problem ?

Your help is appreciated

Upvotes: 0

Views: 1811

Answers (2)

Gsavin
Gsavin

Reputation: 33

If you have namespaces you could always assign it there :

namespace eval blah { 
    variable a 10 
}

proc blah::myproc { } {
    variable a
    puts $a
}
blah::myproc

This way you can avoid potential collisions with other global variables

Upvotes: 0

Googie
Googie

Reputation: 6017

If the variable is declared at the same stack level as the call to myproc then you can do following in your proc:

upvar a a

like this:

set a 10
proc myproc { } {
    upvar a a
    puts $a
}
myproc

and then you can use $a locally in the procedure. The upvar command "links" a variable declared somewhere in the stack with a local variable. If the variable is declared more than 1 level deeper in the stack, thn you need to pass "2" to upvar, so it knows where to look for the variable:

upvar 2 a a

If you don't pass the "2" (or other value), the upvar assumes default lookup depth of 1.

You can read more details about upvar in Tcl documentation for that command.

If the variable a is always a global variable (declared at the script top level), then you can use:

global a

in your procedure, instead of upvar.

Upvotes: 2

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