mirror of https://github.com/mkerrisk/man-pages
120 lines
3.2 KiB
Groff
120 lines
3.2 KiB
Groff
.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.\" References consulted:
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.\" Linux libc source code
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.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
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.\" 386BSD man pages
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.\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
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.\" Modified 2001-04-01 by aeb
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.\" Modified 2003-07-23 by aeb
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.\"
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.TH USLEEP 3 2007-02-01 "" "Linux Programmer's Manual"
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.SH NAME
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usleep \- suspend execution for microsecond intervals
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.SH SYNOPSIS
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.nf
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.B "#define _XOPEN_SOURCE 500 /* Or: #define _BSD_SOURCE */"
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.br
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.B "#include <unistd.h>"
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.sp
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.BI "int usleep(useconds_t " usec );
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.fi
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.SH DESCRIPTION
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The
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.BR usleep ()
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function suspends execution of the calling process for
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(at least) \fIusec\fP microseconds.
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The sleep may be lengthened slightly
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by any system activity or by the time spent processing the call or by the
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granularity of system timers.
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.SH "RETURN VALUE"
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0 on success, \-1 on error.
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.SH ERRORS
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.TP
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.B EINTR
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Interrupted by a signal.
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.TP
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.B EINVAL
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\fIusec\fP is not smaller than 1000000.
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(On systems where that is considered an error.)
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.SH "CONFORMING TO"
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4.3BSD, POSIX.1-2001.
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POSIX.1-2001 declares this function obsolete; use
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.BR nanosleep (2)
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instead.
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On the original BSD implementation,
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and in glibc before version 2.2.2, the return type of this function is
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.IR void .
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The POSIX version returns
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.IR int ,
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and this is also the prototype used since glibc 2.2.2.
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Only the
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.B EINVAL
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error return is documented by SUSv2.
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.SH NOTES
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The type
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.B useconds_t
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is an unsigned integer type capable of holding integers
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in the range [0,1000000].
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Programs will be more portable
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if they never mention this type explicitly.
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Use
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.RS
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.nf
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.ta 8
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.sp
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#include <unistd.h>
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\&...
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unsigned int usecs;
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\&.
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usleep(usecs);
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.fi
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.RE
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.LP
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The interaction of this function with the
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.B SIGALRM
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signal, and with other timer functions such as
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.BR alarm (2),
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.BR sleep (3),
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.BR nanosleep (2),
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.BR setitimer (2),
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.BR timer_create (3),
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.BR timer_delete (3),
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.BR timer_getoverrun (3),
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.BR timer_gettime (3),
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.BR timer_settime (3),
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.BR ualarm (3)
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is unspecified.
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.SH "SEE ALSO"
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.BR alarm (2),
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.BR getitimer (2),
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.BR nanosleep (2),
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.BR select (2),
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.BR setitimer (2),
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.BR ualarm (3),
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.BR sleep (3),
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.BR feature_test_macros (7),
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.BR time (7)
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