This command is part of the [TclX] package.
    :   '''for_file''' ''var filename code''

This command implements a loop over the contents of a file. For each line in ''filename'', it sets ''var'' to the line and executes ''code''.
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Here's how to redo it in [pure-Tcl]:

======
 proc for_file {varName filename body} {
    upvar 1 $varName var
    set fp [open $filename]
    while {[gets $fp var]>=0} {
       uplevel 1 $body
    }
    close $fp
 } ;#
======

[break] and [continue] support would need some extra action, compare [do...until in Tcl].



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