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Full Discussion: Wrapping 'sleep' with my 'resleep' function (Resettable sleep)
Top Forums Shell Programming and Scripting Wrapping 'sleep' with my 'resleep' function (Resettable sleep) Post 302356497 by Corona688 on Friday 25th of September 2009 05:43:47 PM
Old 09-25-2009
That seems an awkward thing to do in shell. It'd also make it difficult to run two instances of sleep. I'd write it in C:
Code:
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <signal.h>
#include <limits.h>

void catch(int c)        {       }

int main(int argc, char *argv[])
{
        unsigned long start=time(NULL), len;

        if(argc != 2)
        {
                fprintf(stderr, "usage: %s 60\n", argv[0]);
                return(1);
        }

        len=atol(argv[1]);

        if((len == LONG_MIN) || (len == LONG_MAX) || (len < 0))
        {
                fprintf(stderr, "Bad input value, must be positive integer\n");
                return(1);
        }

        signal(SIGINT, catch);

        while( (time(NULL) < (start+len)))
        if(sleep((start+len) - time(NULL)))
        {
                int off=INT_MAX;
                signal(SIGINT, SIG_DFL);
                while(off == INT_MAX)
                {
                        printf("\r%d seconds remain, offset:",
                                (start+len)-time(NULL));

                        if(scanf("%d", &off) != 1)
                        {
                                fflush(stdin);
                                off=-1;
                        }
                }

                printf("%d%+d seconds, %d remain\n", len, off,
                        (start+len+off)-time(NULL));
                len += off;

                signal(SIGINT, catch);
        }

        return(0);
}

Run it and hit ctrl-C, and it will show a prompt telling you how much is left then ask for an offset in seconds. A positive number of seconds will add time, a negative number will subtract time. It calculates all this time relative to the program start, so a 'resleep 90', ctrl-c, then adding 25 will have it end precisely 115 seconds after it started even though some seconds may have been spent waiting for you to type. If you hit ctrl-C again instead of entering an offset, it just quits.
Last edited by Corona688; 09-25-2009 at 06:49 PM..
 

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LEARN ABOUT OPENSOLARIS

sleep

sleep(3C)						   Standard C Library Functions 						 sleep(3C)

NAME

       sleep - suspend execution for an interval of time

SYNOPSIS

       #include <unistd.h>

       unsigned int sleep(unsigned int seconds);

DESCRIPTION

       The  caller  is	suspended  from execution for the number of seconds specified by the argument. The actual suspension time may be less than
       that requested because any caught signal will terminate the sleep() following execution of that signal's catching routine.  The	suspension
       time  may  be longer than requested by an arbitrary amount because of the scheduling of other activity in the system. The value returned by
       sleep() will be the ``unslept'' amount (the requested time minus the time actually slept) if the caller incurred premature arousal  because
       of a caught signal.

       The use of the sleep() function has no effect on the action or blockage of any signal. In a multithreaded process, only the invoking thread
       is suspended from execution.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Committed 		   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |Async-Signal-Safe 	   |
       +-----------------------------+-----------------------------+
       |Standard		     |See standards(5). 	   |
       +-----------------------------+-----------------------------+

SEE ALSO

       nanosleep(3C), attributes(5), standards(5)

SunOS 5.11							    5 Feb 2008								 sleep(3C)
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