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1 | .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk) |
2 | .\" | |
93015253 | 3 | .\" %%%LICENSE_START(VERBATIM) |
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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. | |
7 | .\" | |
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. | |
c13182ef | 12 | .\" |
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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14 | .\" manual page may be incorrect or out-of-date.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 | |
19 | .\" professionally. | |
c13182ef | 20 | .\" |
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21 | .\" Formatted or processed versions of this manual, if unaccompanied by |
22 | .\" the source, must acknowledge the copyright and authors of this work. | |
4b72fb64 | 23 | .\" %%%LICENSE_END |
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24 | .\" |
25 | .\" References consulted: | |
26 | .\" Linux libc source code | |
27 | .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991) | |
28 | .\" 386BSD man pages | |
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 | |
32 | .\" | |
4b8c67d9 | 33 | .TH USLEEP 3 2017-09-15 "" "Linux Programmer's Manual" |
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34 | .SH NAME |
35 | usleep \- suspend execution for microsecond intervals | |
36 | .SH SYNOPSIS | |
37 | .nf | |
fea681da | 38 | .B "#include <unistd.h>" |
68e4db0a | 39 | .PP |
c10859eb | 40 | .BI "int usleep(useconds_t " usec ); |
fea681da | 41 | .fi |
68e4db0a | 42 | .PP |
cc4615cc MK |
43 | .in -4n |
44 | Feature Test Macro Requirements for glibc (see | |
45 | .BR feature_test_macros (7)): | |
46 | .in | |
68e4db0a | 47 | .PP |
cc4615cc | 48 | .BR usleep (): |
2df50e3d MK |
49 | .ad l |
50 | .RS 4 | |
51 | .PD 0 | |
52 | .TP 4 | |
53 | Since glibc 2.12: | |
54 | .nf | |
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55 | (_XOPEN_SOURCE\ >=\ 500) && ! (_POSIX_C_SOURCE\ >=\ 200809L) |
56 | || /* Glibc since 2.19: */ _DEFAULT_SOURCE | |
57 | || /* Glibc versions <= 2.19: */ _BSD_SOURCE | |
2df50e3d MK |
58 | .TP 4 |
59 | .fi | |
60 | Before glibc 2.12: | |
cf7fa0a1 MK |
61 | _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500 |
62 | .\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED | |
2df50e3d MK |
63 | .PD |
64 | .RE | |
65 | .ad b | |
fea681da | 66 | .SH DESCRIPTION |
60a90ecd MK |
67 | The |
68 | .BR usleep () | |
ab1d9621 | 69 | function suspends execution of the calling thread for |
c13182ef MK |
70 | (at least) \fIusec\fP microseconds. |
71 | The sleep may be lengthened slightly | |
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72 | by any system activity or by the time spent processing the call or by the |
73 | granularity of system timers. | |
47297adb | 74 | .SH RETURN VALUE |
665637d4 MK |
75 | The |
76 | .BR usleep () | |
77 | function returns 0 on success. | |
78 | On error, \-1 is returned, with | |
79 | .I errno | |
80 | set to indicate the cause of the error. | |
fea681da MK |
81 | .SH ERRORS |
82 | .TP | |
097585ed | 83 | .B EINTR |
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84 | Interrupted by a signal; see |
85 | .BR signal (7). | |
fea681da | 86 | .TP |
097585ed | 87 | .B EINVAL |
3ca4400d | 88 | \fIusec\fP is greater than or equal to 1000000. |
fea681da | 89 | (On systems where that is considered an error.) |
e0fc49a4 | 90 | .SH ATTRIBUTES |
b4f53c94 PH |
91 | For an explanation of the terms used in this section, see |
92 | .BR attributes (7). | |
93 | .TS | |
94 | allbox; | |
95 | lb lb lb | |
96 | l l l. | |
97 | Interface Attribute Value | |
98 | T{ | |
e0fc49a4 | 99 | .BR usleep () |
b4f53c94 PH |
100 | T} Thread safety MT-Safe |
101 | .TE | |
47297adb | 102 | .SH CONFORMING TO |
68e1685c | 103 | 4.3BSD, POSIX.1-2001. |
5a7f195c MK |
104 | POSIX.1-2001 declares this function obsolete; use |
105 | .BR nanosleep (2) | |
106 | instead. | |
f8eabcf9 MK |
107 | POSIX.1-2008 removes the specification of |
108 | .BR usleep (). | |
847e0d88 | 109 | .PP |
c13182ef | 110 | On the original BSD implementation, |
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111 | and in glibc before version 2.2.2, the return type of this function is |
112 | .IR void . | |
c13182ef MK |
113 | The POSIX version returns |
114 | .IR int , | |
5a7f195c | 115 | and this is also the prototype used since glibc 2.2.2. |
847e0d88 | 116 | .PP |
1274071a MK |
117 | Only the |
118 | .B EINVAL | |
f041c2fd | 119 | error return is documented by SUSv2 and POSIX.1-2001. |
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120 | .SH NOTES |
121 | The type | |
f19a0f03 | 122 | .I useconds_t |
fea681da | 123 | is an unsigned integer type capable of holding integers |
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124 | in the range [0,1000000]. |
125 | Programs will be more portable | |
126 | if they never mention this type explicitly. | |
127 | Use | |
bdd915e2 | 128 | .PP |
a6e2f128 | 129 | .in +4n |
bdd915e2 | 130 | .EX |
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131 | #include <unistd.h> |
132 | \&... | |
5a7f195c | 133 | unsigned int usecs; |
74d32233 | 134 | \&... |
5a7f195c | 135 | usleep(usecs); |
bdd915e2 | 136 | .EE |
a6e2f128 | 137 | .in |
dd3568a1 | 138 | .PP |
8bd58774 MK |
139 | The interaction of this function with the |
140 | .B SIGALRM | |
141 | signal, and with other timer functions such as | |
cbe7b8d1 | 142 | .BR alarm (2), |
fb186734 MK |
143 | .BR sleep (3), |
144 | .BR nanosleep (2), | |
145 | .BR setitimer (2), | |
804f03e6 MK |
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), | |
fb186734 | 151 | .BR ualarm (3) |
fea681da | 152 | is unspecified. |
47297adb | 153 | .SH SEE ALSO |
28131cd9 | 154 | .BR alarm (2), |
fea681da MK |
155 | .BR getitimer (2), |
156 | .BR nanosleep (2), | |
157 | .BR select (2), | |
158 | .BR setitimer (2), | |
50e5322c | 159 | .BR sleep (3), |
f0c34053 | 160 | .BR ualarm (3), |
5a7f195c | 161 | .BR time (7) |