http://www.purl.org/tcl/home/man/tcl8.4/TkCmd/getOpenFile.htm
Note: Unlike most Tk widgets, this widget's name (getOpenFile) is not the same as its creation command (tk_getOpenFile).
tkfbox [L1 ] is a nifty little portable bundle for extending get{Open,Save}File capabilities.
Tk syntax help - Arts and crafts of Tcl-Tk programming - Category Command