USLEEP(3)              FreeBSD Library Functions Manual              USLEEP(3)

NAME
     usleep - suspend thread execution for an interval measured in
     microseconds

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <unistd.h>

     int
     usleep(useconds_t microseconds);

DESCRIPTION
     The usleep() function suspends execution of the calling thread until
     either microseconds microseconds have elapsed or a signal is delivered to
     the thread and its action is to invoke a signal-catching function or to
     terminate the process.  System activity may lengthen the sleep by an
     indeterminate amount.

     This function is implemented using nanosleep(2) by pausing for
     microseconds microseconds or until a signal occurs.  Consequently, in
     this implementation, sleeping has no effect on the state of process
     timers, and there is no special handling for SIGALRM.

RETURN VALUES
     The usleep() function returns the value 0 if successful; otherwise the
     value -1 is returned and the global variable errno is set to indicate the
     error.

ERRORS
     The usleep() function will fail if:

     [EINTR]            A signal was delivered to the calling thread and its
                        action was to invoke a signal-catching function.

SEE ALSO
     nanosleep(2), sleep(3)

HISTORY
     The usleep() function appeared in 4.3BSD.

FreeBSD 13.1-RELEASE-p6        February 11, 2021       FreeBSD 13.1-RELEASE-p6