usleep(3) - NetBSD Manual Pages

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USLEEP(3)               NetBSD Library Functions Manual              USLEEP(3)


NAME

     usleep -- suspend execution for interval of microseconds


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #include <unistd.h>

     int
     usleep(useconds_t microseconds);


DESCRIPTION

     This interface is obsoleted by nanosleep(2).

     The usleep() function suspends execution of the calling process until
     either the number of microseconds specified by microseconds have elapsed
     or a signal is delivered to the calling process and its action is to
     invoke a signal catching function or to terminate the process.  The sus-
     pension time may be longer than requested due to the scheduling of other
     activity by the system.


RETURN VALUES

     On successful completion, usleep() returns 0.  Otherwise, it returns -1
     and sets errno to indicate the error.


ERRORS

     The usleep() function may fail if:

     [EINTR]            usleep was interrupted by the delivery of a signal.


SEE ALSO

     nanosleep(2), sleep(3)


STANDARDS

     The usleep() function conforms to X/Open Portability Guide Issue 4,
     Version 2 (``XPG4.2'').  It later appeared in the POSIX standard, but in
     IEEE Std 1003.1-2004 (``POSIX.1'') it was marked as legacy and the use of
     nanosleep(2) was recommended instead.  The IEEE Std 1003.1-2008
     (``POSIX.1'') revision removed usleep() from the specification.


HISTORY

     The usleep() function appeared in 4.3BSD.


CAVEATS

     In IEEE Std 1003.1-2004 (``POSIX.1''), usleep was limited to values of
     microseconds less than one million.  Some implementations, including
     NetBSD before 10.1, fail immediately with EINVAL -- and don't sleep at
     all -- if microseconds is one million or greater.

NetBSD 10.1                     April 22, 2024                     NetBSD 10.1