nanosleep
TLDR
Sleep for 1 second (C code)
$ struct timespec ts = {1, 0}; nanosleep(&ts, NULL);
Sleep for 500 milliseconds$ struct timespec ts = {0, 500000000L}; nanosleep(&ts, NULL);
Sleep with remaining time$ nanosleep(&req, &rem);
SYNOPSIS
int nanosleep(const struct timespec *req, struct timespec *rem)
DESCRIPTION
nanosleep suspends execution of the calling thread for the specified duration. Unlike sleep(), it provides nanosecond precision and handles interruption gracefully.
The function returns immediately if interrupted by a signal, storing remaining time in rem.
PARAMETERS
req
Requested sleep time (seconds and nanoseconds).rem
Remaining time if interrupted (can be NULL).
EXAMPLE
$ #include <time.h>
int main() {
struct timespec req = {0, 100000000L}; // 100ms
struct timespec rem;
while (nanosleep(&req, &rem) == -1) {
req = rem; // Continue sleeping
}
return 0;
}
int main() {
struct timespec req = {0, 100000000L}; // 100ms
struct timespec rem;
while (nanosleep(&req, &rem) == -1) {
req = rem; // Continue sleeping
}
return 0;
}
TIMESPEC STRUCTURE
$ struct timespec {
time_t tv_sec; // Seconds
long tv_nsec; // Nanoseconds (0-999999999)
};
time_t tv_sec; // Seconds
long tv_nsec; // Nanoseconds (0-999999999)
};
CAVEATS
Actual resolution depends on system clock. May sleep slightly longer than requested. EINTR on signal delivery.
HISTORY
nanosleep was introduced in POSIX.1-2001 to provide high-resolution sleep functionality beyond the second granularity of sleep().
SEE ALSO
sleep(3), usleep(3), clock_nanosleep(2), select(2)
