SLEEP

• Source: https://www.freebasic.net/wiki/wikka.php?wakka=KeyPgSleep
• Last revised: 2023-05-28

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Waits until a specified time has elapsed, or a key is pressed.

Syntax

declare sub Sleep ( byval amount as long = -1 )
declare function Sleep ( byval amount as long , byval keyflag as long ) as long

Usage

Sleep [ amount [, keyflag ]]
result = Sleep ( amount, keyflag )

Parameters

amount

Optional number of milliseconds to wait (default is to wait for a key press).

keyflag

Optional flag; give it a value of 0 for a normal sleep, or 1 to specify that the wait cannot be interrupted by a key press.

Return Value

Returns 1 if keyflag was not a valid value (i.e. something other than 0 or 1) to indicate failure, or 0 otherwise.

Description

Sleep will wait until amount milliseconds (can be seconds in -lang qb, see below) given elapsed (if any value was passed) or until the user presses a key. If amount is below 100 ms then Sleep will always wait the full requested amount (key presses are ignored).

Include the second parameter, 1, for a "deep" sleep, which cannot be interrupted by pressing a key.

The accuracy of Sleep is variable depending on the OS cycle time:

Windows NT/2K/XP: 15 ms, 9x/Me: 50 ms, Linux: 10ms, DOS: 55 ms.

And using for the amount parameter values lower than these accuracy values does not allow Sleep to produce the corresponding wait values (always higher wait, and of the order of these values) except for the amount value '0'.

Call Sleep with 25ms or less to release time-slice when waiting for user input or looping inside a thread. This will prevent the program from unnecessarily hogging the CPU.

Sleep does not clear the keyboard input buffer and any keys pressed during a call to Sleep are retained and can be later read by Inkey or Getkey or Input.

When Sleep has no parameters (waiting for a key pressed only), Getkey keyword can be used instead of Sleep.

For the general form of Sleep (with parameters), if the user want to clear the keyboard input buffer from any eventual keys pressed during the Sleep execution, he can use after the Sleep instruction line something like the following method:

start GeSHi

While Inkey <> "": Wend  '' loop until the keyboard input buffer is empty

end GeSHi

Examples

start GeSHi

Print "press a key"
Sleep
GetKey  '' clear the keyboard input buffer, and even in that code case, the 'Sleep' keyword can be outright omitted
Print "waiting half second"
Sleep 500

end GeSHi

start GeSHi

Dim As String s

Print "wait 3 seconds or press a key"
Sleep 3000
Print "outputed by timeout or key pressed"
While Inkey <> ""  '' loop until the keyboard input buffer is empty
Wend

Input "enter a string"; s
Print "string entered: " & "'" & s & "'"

Sleep

end GeSHi

Dialect Differences

• In the -lang fb and -lang fblite dialects, the amount value is in milliseconds.
• In the -lang qb dialect, the amount value is in seconds as in QB. If the second parameter keyflag is given, or the keyword is written as __Sleep the value is expected to be in milliseconds.

Differences from QB

• None in the -lang qb dialect.
• In QB, the delay was given in whole seconds only and did not support the keyflag parameter.

See also

• Timer
• Inkey

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