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Linux / Unix Command: nanosleep
Command Library


nanosleep - pause execution for a specified time  


#include <time.h>

int nanosleep(const struct timespec *req, struct timespec *rem);  


nanosleep delays the execution of the program for at least the time specified in *req. The function can return earlier if a signal has been delivered to the process. In this case, it returns -1, sets errno to EINTR, and writes the remaining time into the structure pointed to by rem unless rem is NULL. The value of *rem can then be used to call nanosleep again and complete the specified pause.

The structure timespec is used to specify intervals of time with nanosecond precision. It is specified in <time.h> and has the form

struct timespec
        time_t  tv_sec;         /* seconds */
        long    tv_nsec;        /* nanoseconds */

The value of the nanoseconds field must be in the range 0 to 999 999 999.

Compared to sleep(3) and usleep(3), nanosleep has the advantage of not affecting any signals, it is standardized by POSIX, it provides higher timing resolution, and it allows to continue a sleep that has been interrupted by a signal more easily.  


In case of an error or exception, the nanosleep system call returns -1 instead of 0 and sets errno to one of the following values:
The pause has been interrupted by a non-blocked signal that was delivered to the process. The remaining sleep time has been written into *rem so that the process can easily call nanosleep again and continue with the pause.
The value in the tv_nsec field was not in the range 0 to 999 999 999 or tv_sec was negative.


sleep(3), usleep(3), sched_setscheduler(2), timer_create(2)

Important: Use the man command (% man) to see how a command is used on your particular computer.

>> Linux/Unix Command Library

>> Shell Command Library

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