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From: saito <saitology9@gmail.com>
Newsgroups: comp.lang.tcl
Subject: Re: Seeking help with a time calculation
Date: Sun, 1 Dec 2024 15:43:28 -0500
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On 11/29/2024 12:10 PM, Kenny McCormack wrote:
> Platform is Linux.
> 
> In an Expect script, I want to calculate the number of seconds until the
> next "X minutes after the hour".  E.g., if X is 37 and the current time is
> 15:30:30, then the result I seek would be: 390.  If X is 37, and the
> current time is 15:50, then the result would be: 2820.
> 
> It's the number of seconds I have to wait (sleep) until that time arrives.
> 
> I have a method in AWK, which I can (and do) call from my Expect script,
> but I am curious if there is a (simple) native Tcl way to do it.

I think this does the calculation you want. There is an interesting 
"octal" problem left as an exercise :-)

proc wait_how_long {x} {
  set now [clock seconds]
  set mins [clock format $now -format "%M"]
  set secs [clock format $now -format "%S"]

  if {$mins == $x} {
    # in the minute requested
    set wait 0

  } elseif {$mins < $x} {
    # minute has passed
    # add one hour
    set wait [expr {($x - $mins - 1) * 60 + (60 - $secs)}]

  } else {
    # some minutes ahead, within the same hour
    set mindiff [expr {(60 - $mins - 1) + $x}]
    set wait [expr {$mindiff * 60 + (60 - $secs)}]
  }

  return $wait
}