How can I redirect stdout into a file in tcl

Question

how can I redirect a proc output into a file in tcl, for example, I have a proc foo, and would like to redirect the foo output into a file bar. But got this result

Answer 1

Thanks for sharing CFI. I would like to contribute as well. so, i made some changes to redefine puts on dump to file on startlog and end logging on endlog to file when ever we want. This will print on stdout and also redirect stdout to file.

proc startlog {filename } {
    rename puts ::tcl::orig::puts

    set mode w
    global def destination logfilename
    set destination [open $filename $mode]
    set logfilename $filename

    proc puts args "
        uplevel 2 \"::tcl::orig::puts \$args\"
        uplevel \"::tcl::orig::puts $destination \{\$args\}\"; return
    "
}

proc endlog { } {
    global def destination logfilename  
    close $destination
    rename puts {}
    rename ::tcl::orig::puts puts
    cleanlog $logfilename
    puts "name of log file is $logfilename"
}

proc cleanlog {filename } {  
    set f [open $filename]
    set output [open $filename\.log w]
    set line1 [regsub -all {\-nonewline stdout \{} [read $f] ""]
    set line2 [regsub -all {stdout \{} $line1 ""]
    set line3 [regsub -all {\}} $line2 ""]
    set line4 [regsub -all {\{} $line3 ""]
    puts $output $line4
    close $output
    file rename -force $filename.log $filename
}