如何在 C 语言中使用 nanossleep() ? 什么是‘ tim.tv_sec’和‘ tim.tv_nsec’？

tim.tv_sec和 tim.tv_nsec在以下方面的用途是什么？

如何睡眠执行 500000微秒？

#include <stdio.h>
#include <time.h>


int main()
{
struct timespec tim, tim2;
tim.tv_sec = 1;
tim.tv_nsec = 500;


if(nanosleep(&tim , &tim2) < 0 )
{
printf("Nano sleep system call failed \n");
return -1;
}


printf("Nano sleep successfull \n");


return 0;
}
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500000 microseconds are 500000000 nanoseconds. You only wait for 500 ns = 0.5 µs.

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最佳答案

Half a second is 500,000,000 nanoseconds, so your code should read:

tim.tv_sec  = 0;
tim.tv_nsec = 500000000L;

As things stand, you code is sleeping for 1.0000005s (1s + 500ns).

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tv_nsec is the sleep time in nanoseconds. 500000us = 500000000ns, so you want:

nanosleep((const struct timespec[])\{\{0, 500000000L}}, NULL);
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I usually use some #define and constants to make the calculation easy:

#define NANO_SECOND_MULTIPLIER  1000000  // 1 millisecond = 1,000,000 Nanoseconds
const long INTERVAL_MS = 500 * NANO_SECOND_MULTIPLIER;

Hence my code would look like this:

timespec sleepValue = {0};


sleepValue.tv_nsec = INTERVAL_MS;
nanosleep(&sleepValue, NULL);
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This worked for me ....

#include <stdio.h>
#include <time.h>   /* Needed for struct timespec */




int mssleep(long miliseconds)
{
struct timespec rem;
struct timespec req= {
(int)(miliseconds / 1000),     /* secs (Must be Non-Negative) */
(miliseconds % 1000) * 1000000 /* nano (Must be in range of 0 to 999999999) */
};


return nanosleep(&req , &rem);
}


int main()
{
int ret = mssleep(2500);
printf("sleep result %d\n",ret);
return 0;
}
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POSIX 7

First find the function: http://pubs.opengroup.org/onlinepubs/9699919799/functions/nanosleep.html

That contains a link to a time.h, which as a header should be where structs are defined:

The header shall declare the timespec structure, which shall > include at least the following members:

time_t  tv_sec    Seconds.
long    tv_nsec   Nanoseconds.

man 2 nanosleep

Pseudo-official glibc docs which you should always check for syscalls:

struct timespec {
time_t tv_sec;        /* seconds */
long   tv_nsec;       /* nanoseconds */
};
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More correct variant:

{
struct timespec delta = {5 /*secs*/, 135 /*nanosecs*/};
while (nanosleep(&delta, &delta));
}

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