CODEWITHSUNDEEP
tcl
Centos Newbie
Centos Newbie

Reputation: 59

Tcl Timer Snippet

I need to print out countdown timer for the time my script sleeps.

Screen output looks like this - 

Started Script

Script will Sleep for 100 seconds

Time left 100
Time left 99
Time left 98

I want print the Time left but by erasing the previous entry.

at time 0

Started Script

Script will Sleep for 100 seconds

Time left 100

at time 1

Started Script

Script will Sleep for 100 seconds

Time left 99

at time 2

Started Script

Script will Sleep for 100 seconds

Time left 98

How can I do this in tcl?

Upvotes: 1

Views: 1306

Answers (1)

Donal Fellows
Donal Fellows

Reputation: 137807

The simplest way to do this is with some terminal tricks. The key trick is that printing a carriage return (\u000d or \r) sends the cursor back to the start of the current line.

puts "Started Script\n"

# Turn off output buffering; important!
fconfigure stdout -buffering none

puts "Script will sleep for 100 seconds\n"

set deadline [expr {[clock seconds] + 100}]
while 1 {
    set now [clock seconds]
    if {$deadline <= $now} {
        break
    }

    # Tricky; the CR is critical to making this work...
    puts -nonewline "\rTime left [expr {$deadline - $now}] "

    # Sleep *half* a second for accuracy
    after 500
}

# Blank the countdown line and put a finished message with a cheap hack
puts -nonewline "[string repeat " " 15]\rDone!"

You can get a more accurate countdown by using clock milliseconds as your timing source and shortening the sleep in after; you'll need some (small amount of) extra work to convert the time remaining to seconds in that case.

Upvotes: 2

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