Training, Open Source computer languages
PerlPHPPythonMySQLApache / TomcatTclRubyJavaC and C++LinuxCSS 
Search for:
Home Accessibility Courses Diary The Mouth Forum Resources Site Map About Us Contact
For 2021 - online Python 3 training - see ((here)).

Our plans were to retire in summer 2020 and see the world, but Coronavirus has lead us into a lot of lockdown programming in Python 3 and PHP 7.
We can now offer tailored online training - small groups, real tutors - works really well for groups of 4 to 14 delegates. Anywhere in the world; course language English.

Please ask about private 'maintenance' training for Python 2, Tcl, Perl, PHP, Lua, etc.
TK error - button command within a procedure

Posted by dvorak_user (dvorak_user), 12 January 2008
edit: I sidestepped the issue and got my program to run properly, but I'd still like an answer. Much appreciated!

Hello, all! I'm working on a script with a portion similar to the code below. I can't get it to work quite right, however.

version 1:
proc something {} {
     set dir "C:\\"
     button .b -text "press me" -command {set temp [tk_getOpenFile -initialdir $dir]}
     pack .b

result: when button is pressed, I get 'Error: can't read "dir": no such variable'

version 2:
proc something {} {
     set dir "C:\\"
     button .b -text "press me" -command "set temp [tk_getOpenFile -initialdir $dir]"
     pack .b

result: prompted to choose a file before button loads.

I really don't know where this script is going wrong, and any help would be appreciated. Thank you!

Posted by admin (Graham Ellis), 13 January 2008
An excellent question.

Curly braces are a deferred block, so the command is stored as you define it and is evaluated later on (and in the root or global context).   But double quoted, the block is evaluated at the time that the proc is run and the component is defined, and in the scope of the proc.

Posted by dvorak_user (dvorak_user), 13 January 2008
Thanks for your explanation - that certainly cleared things up! Much obliged.

This page is a thread posted to the opentalk forum at and archived here for reference. To jump to the archive index please follow this link.

You can Add a comment or ranking to this page

© WELL HOUSE CONSULTANTS LTD., 2022: Well House Manor • 48 Spa Road • Melksham, Wiltshire • United Kingdom • SN12 7NY
PH: 01144 1225 708225 • FAX: 01144 1225 793803 • EMAIL: • WEB: • SKYPE: wellho