| .\" Copyright (c) 1993 by Thomas Koenig (ig25@rz.uni-karlsruhe.de) |
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| .\" Modified Sat Jul 24 18:16:02 1993 by Rik Faith (faith@cs.unc.edu) |
| .TH SLEEP 3 2021-03-22 "GNU" "Linux Programmer's Manual" |
| .SH NAME |
| sleep \- sleep for a specified number of seconds |
| .SH SYNOPSIS |
| .nf |
| .B #include <unistd.h> |
| .PP |
| .BI "unsigned int sleep(unsigned int " "seconds" ); |
| .fi |
| .SH DESCRIPTION |
| .BR sleep () |
| causes the calling thread to sleep either until |
| the number of real-time seconds specified in |
| .I seconds |
| have elapsed or until a signal arrives which is not ignored. |
| .SH RETURN VALUE |
| Zero if the requested time has elapsed, |
| or the number of seconds left to sleep, |
| if the call was interrupted by a signal handler. |
| .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 sleep () |
| T} Thread safety MT-Unsafe sig:SIGCHLD/linux |
| .TE |
| .hy |
| .ad |
| .sp 1 |
| .SH CONFORMING TO |
| POSIX.1-2001, POSIX.1-2008. |
| .SH NOTES |
| On Linux, |
| .BR sleep () |
| is implemented via |
| .BR nanosleep (2). |
| See the |
| .BR nanosleep (2) |
| man page for a discussion of the clock used. |
| .SS Portability notes |
| On some systems, |
| .BR sleep () |
| may be implemented using |
| .BR alarm (2) |
| and |
| .BR SIGALRM |
| (POSIX.1 permits this); |
| mixing calls to |
| .BR alarm (2) |
| and |
| .BR sleep () |
| is a bad idea. |
| .PP |
| Using |
| .BR longjmp (3) |
| from a signal handler or modifying the handling of |
| .B SIGALRM |
| while sleeping will cause undefined results. |
| .SH SEE ALSO |
| .BR sleep (1), |
| .BR alarm (2), |
| .BR nanosleep (2), |
| .BR signal (2), |
| .BR signal (7) |