1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
3 .\" %%%LICENSE_START(VERBATIM)
4 .\" Permission is granted to make and distribute verbatim copies of this
5 .\" manual provided the copyright notice and this permission notice are
6 .\" preserved on all copies.
8 .\" Permission is granted to copy and distribute modified versions of this
9 .\" manual under the conditions for verbatim copying, provided that the
10 .\" entire resulting derived work is distributed under the terms of a
11 .\" permission notice identical to this one.
13 .\" Since the Linux kernel and libraries are constantly changing, this
14 .\" manual page may be incorrect or out-of-date. The author(s) assume no
15 .\" responsibility for errors or omissions, or for damages resulting from
16 .\" the use of the information contained herein. The author(s) may not
17 .\" have taken the same level of care in the production of this manual,
18 .\" which is licensed free of charge, as they might when working
21 .\" Formatted or processed versions of this manual, if unaccompanied by
22 .\" the source, must acknowledge the copyright and authors of this work.
25 .\" References consulted:
26 .\" Linux libc source code
27 .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
29 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
30 .\" Modified 2001-04-01 by aeb
31 .\" Modified 2003-07-23 by aeb
33 .TH USLEEP 3 2017-09-15 "" "Linux Programmer's Manual"
35 usleep \- suspend execution for microsecond intervals
38 .B "#include <unistd.h>"
40 .BI "int usleep(useconds_t " usec );
44 Feature Test Macro Requirements for glibc (see
45 .BR feature_test_macros (7)):
55 (_XOPEN_SOURCE\ >=\ 500) && ! (_POSIX_C_SOURCE\ >=\ 200809L)
56 || /* Glibc since 2.19: */ _DEFAULT_SOURCE
57 || /* Glibc versions <= 2.19: */ _BSD_SOURCE
61 _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500
62 .\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
69 function suspends execution of the calling thread for
70 (at least) \fIusec\fP microseconds.
71 The sleep may be lengthened slightly
72 by any system activity or by the time spent processing the call or by the
73 granularity of system timers.
77 function returns 0 on success.
78 On error, \-1 is returned, with
80 set to indicate the cause of the error.
84 Interrupted by a signal; see
88 \fIusec\fP is greater than or equal to 1000000.
89 (On systems where that is considered an error.)
91 For an explanation of the terms used in this section, see
97 Interface Attribute Value
100 T} Thread safety MT-Safe
103 4.3BSD, POSIX.1-2001.
104 POSIX.1-2001 declares this function obsolete; use
107 POSIX.1-2008 removes the specification of
110 On the original BSD implementation,
111 and in glibc before version 2.2.2, the return type of this function is
113 The POSIX version returns
115 and this is also the prototype used since glibc 2.2.2.
119 error return is documented by SUSv2 and POSIX.1-2001.
123 is an unsigned integer type capable of holding integers
124 in the range [0,1000000].
125 Programs will be more portable
126 if they never mention this type explicitly.
139 The interaction of this function with the
141 signal, and with other timer functions such as
146 .BR timer_create (2),
147 .BR timer_delete (2),
148 .BR timer_getoverrun (2),
149 .BR timer_gettime (2),
150 .BR timer_settime (2),