| .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk) |
| .\" |
| .\" %%%LICENSE_START(VERBATIM) |
| .\" Permission is granted to make and distribute verbatim copies of this |
| .\" manual provided the copyright notice and this permission notice are |
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| .\" Permission is granted to copy and distribute modified versions of this |
| .\" manual under the conditions for verbatim copying, provided that the |
| .\" entire resulting derived work is distributed under the terms of a |
| .\" permission notice identical to this one. |
| .\" |
| .\" Since the Linux kernel and libraries are constantly changing, this |
| .\" manual page may be incorrect or out-of-date. The author(s) assume no |
| .\" responsibility for errors or omissions, or for damages resulting from |
| .\" the use of the information contained herein. The author(s) may not |
| .\" have taken the same level of care in the production of this manual, |
| .\" which is licensed free of charge, as they might when working |
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| .\" Formatted or processed versions of this manual, if unaccompanied by |
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| .\" %%%LICENSE_END |
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| .\" References consulted: |
| .\" Linux libc source code |
| .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991) |
| .\" 386BSD man pages |
| .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu) |
| .\" Modified 2001-04-01 by aeb |
| .\" Modified 2003-07-23 by aeb |
| .\" |
| .TH USLEEP 3 2021-03-22 "" "Linux Programmer's Manual" |
| .SH NAME |
| usleep \- suspend execution for microsecond intervals |
| .SH SYNOPSIS |
| .nf |
| .B "#include <unistd.h>" |
| .PP |
| .BI "int usleep(useconds_t " usec ); |
| .fi |
| .PP |
| .RS -4 |
| Feature Test Macro Requirements for glibc (see |
| .BR feature_test_macros (7)): |
| .RE |
| .PP |
| .BR usleep (): |
| .nf |
| Since glibc 2.12: |
| (_XOPEN_SOURCE >= 500) && ! (_POSIX_C_SOURCE >= 200809L) |
| || /* Glibc since 2.19: */ _DEFAULT_SOURCE |
| || /* Glibc <= 2.19: */ _BSD_SOURCE |
| Before glibc 2.12: |
| _BSD_SOURCE || _XOPEN_SOURCE >= 500 |
| .\" || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED |
| .fi |
| .SH DESCRIPTION |
| The |
| .BR usleep () |
| function suspends execution of the calling thread for |
| (at least) \fIusec\fP microseconds. |
| The sleep may be lengthened slightly |
| by any system activity or by the time spent processing the call or by the |
| granularity of system timers. |
| .SH RETURN VALUE |
| The |
| .BR usleep () |
| function returns 0 on success. |
| On error, \-1 is returned, with |
| .I errno |
| set to indicate the error. |
| .SH ERRORS |
| .TP |
| .B EINTR |
| Interrupted by a signal; see |
| .BR signal (7). |
| .TP |
| .B EINVAL |
| \fIusec\fP is greater than or equal to 1000000. |
| (On systems where that is considered an error.) |
| .SH ATTRIBUTES |
| For an explanation of the terms used in this section, see |
| .BR attributes (7). |
| .ad l |
| .nh |
| .TS |
| allbox; |
| lbx lb lb |
| l l l. |
| Interface Attribute Value |
| T{ |
| .BR usleep () |
| T} Thread safety MT-Safe |
| .TE |
| .hy |
| .ad |
| .sp 1 |
| .SH CONFORMING TO |
| 4.3BSD, POSIX.1-2001. |
| POSIX.1-2001 declares this function obsolete; use |
| .BR nanosleep (2) |
| instead. |
| POSIX.1-2008 removes the specification of |
| .BR usleep (). |
| .PP |
| On the original BSD implementation, |
| and in glibc before version 2.2.2, the return type of this function is |
| .IR void . |
| The POSIX version returns |
| .IR int , |
| and this is also the prototype used since glibc 2.2.2. |
| .PP |
| Only the |
| .B EINVAL |
| error return is documented by SUSv2 and POSIX.1-2001. |
| .SH NOTES |
| The type |
| .I useconds_t |
| is an unsigned integer type capable of holding integers |
| in the range [0,1000000]. |
| Programs will be more portable |
| if they never mention this type explicitly. |
| Use |
| .PP |
| .in +4n |
| .EX |
| #include <unistd.h> |
| \&... |
| unsigned int usecs; |
| \&... |
| usleep(usecs); |
| .EE |
| .in |
| .PP |
| The interaction of this function with the |
| .B SIGALRM |
| signal, and with other timer functions such as |
| .BR alarm (2), |
| .BR sleep (3), |
| .BR nanosleep (2), |
| .BR setitimer (2), |
| .BR timer_create (2), |
| .BR timer_delete (2), |
| .BR timer_getoverrun (2), |
| .BR timer_gettime (2), |
| .BR timer_settime (2), |
| .BR ualarm (3) |
| is unspecified. |
| .SH SEE ALSO |
| .BR alarm (2), |
| .BR getitimer (2), |
| .BR nanosleep (2), |
| .BR select (2), |
| .BR setitimer (2), |
| .BR sleep (3), |
| .BR ualarm (3), |
| .BR time (7) |