An alternative wait function?

**Nanor** · 01-07-2007

Hey, I just joined the forums and I thought I'd dive straight in with a query. I am searching for a function that will wait, say 5 seconds, and then proceed with whatever comes next. For example:

cout << "Please wait\n";

<Some sort of pause function>

cout << "Did you enjoy your wait?\n";

Apparently, wait just waits until background processes are finished. The exact definition I found was "With no arguments, the wait command waits until all background processes known to the current shell have terminated".

Are there some arguments I need to add, or is a totally different function needed?

Thank you

**Salem** · 01-07-2007

Eg.
cout << "hello\n";
sleep(5);
cout << "world\n";

**Oldman47** · 01-07-2007

The <time.h> lib. can do that. wait (int); where int is equal to seconds.

**Nanor** · 01-07-2007

Originally Posted by Salem

Eg.
cout << "hello\n";
sleep(5);
cout << "world\n";

When I use this I get the error " `sleep' cannot be used as a function ". I also get the same for wait.

**l2u** · 01-07-2007

Include windows.h for Sleep().

I wonder why some professionals try to avoid Sleep function?

**Oldman47** · 01-07-2007

I wasn't aware of Sleep() (and about a million other snipets of code).

Wait (); doesn't work by itself. I somewhat assumed that you'd go research.

Code:

void wait ( int seconds )
{
  clock_t endwait;
  endwait = clock () + seconds * CLK_TCK ;
  while (clock() < endwait) {}
}

**Salem** · 01-07-2007

Of course, actually posting
a) your code
b) your OS/Compiler
might make it a lot easier to figure out what your question is.

And when I say code, I mean all of it, not random single lines.

**anon** · 01-07-2007

The bad thing with the wait function is that it is a tight loop that uses up all free CPU resources. Sleep may only work for Windows, but at least it doesn't use CPU to do nothing.

**CornedBee** · 01-07-2007

There is no portable solution that doesn't use busy waiting (i.e. a loop that just executes until a certain point in time is reached, which is bad because it hogs the CPU for no reason).

Therefore, in this case it would be better to write a small wait() function yourself that calls different functions depending on the platform.
xp_sleep.h:

Code:

void xp_sleep(unsigned int seconds);
void xp_millisleep(unsigned int milliseconds);

xp_sleep_win32.cpp:

Code:

#include <windows.h>
void xp_sleep(unsigned int seconds)
{
  Sleep(seconds * 1000);
}

void xp_millisleep(unsigned int milliseconds)
{
  Sleep(milliseconds);
}

xp_sleep_posix.cpp:

Code:

#define _POSIX_C_SOURCE 199309
#include <errno.h>
#include <time.h>

void xp_sleep(unsigned int seconds)
{
  struct timespec ts = {
    seconds,
    0L
  };
  while(nanosleep(&ts, &ts) == -1 && errno == EINTR) {
  }
}
void xp_millisleep(unsigned int milliseconds)
{
  struct timespec ts = {
    milliseconds / 1000,
    (milliseconds % 1000) * 1000000L
  };
  while(nanosleep(&ts, &ts) == -1 && errno == EINTR) {
  }
}

Then use the posix implementation for all Unix variants (including Mac OS X) and the win32 for Windows.

Usage:

Code:

#include "xp_sleep.h"

int main()
{
  xp_sleep(5);
  return 0;
}

Note: although this is the C++ forum, I've intentionally kept this code fully compatible with both C and C++.

**Nanor** · 01-07-2007

Unfortunately I was under the impression it would be as simple as wait(5). Hehe, well, I'll leave it until I get a bit more familiar with C++. Thanks everyone.

**anon** · 01-08-2007

If you don't care about portability and want to work it with Windows, you can just call the Sleep() function. It would be good to know that your program cannot be compiled for other OS without modifications, but I guess for a new-comer and a learner supporting all platforms is not so important.

**dwks** · 01-08-2007

There is an FAQ on the subject . . . http://faq.cprogramming.com/cgi-bin/...&id=1043284392 . . . it has less information than this thread, though.

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