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1 | .\" Hey Emacs! This file is -*- nroff -*- source. |
| 2 | .\" | |
| 3 | .\" This manpage is Copyright (C) 1992 Drew Eckhardt; | |
| 4 | .\" 1993 Michael Haardt, Ian Jackson. | |
| 5 | .\" | |
| 6 | .\" Permission is granted to make and distribute verbatim copies of this | |
| 7 | .\" manual provided the copyright notice and this permission notice are | |
| 8 | .\" preserved on all copies. | |
| 9 | .\" | |
| 10 | .\" Permission is granted to copy and distribute modified versions of this | |
| 11 | .\" manual under the conditions for verbatim copying, provided that the | |
| 12 | .\" entire resulting derived work is distributed under the terms of a | |
| 13 | .\" permission notice identical to this one. | |
| 14 | .\" | |
| 15 | .\" Since the Linux kernel and libraries are constantly changing, this | |
| 16 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
| 17 | .\" responsibility for errors or omissions, or for damages resulting from | |
| 18 | .\" the use of the information contained herein. The author(s) may not | |
| 19 | .\" have taken the same level of care in the production of this manual, | |
| 20 | .\" which is licensed free of charge, as they might when working | |
| 21 | .\" professionally. | |
| 22 | .\" | |
| 23 | .\" Formatted or processed versions of this manual, if unaccompanied by | |
| 24 | .\" the source, must acknowledge the copyright and authors of this work. | |
| 25 | .\" | |
| 26 | .\" Modified Wed Jul 21 19:42:57 1993 by Rik Faith <faith@cs.unc.edu> | |
| 27 | .\" Modified Sun Jul 21 21:25:26 1996 by Andries Brouwer <aeb@cwi.nl> | |
| 28 | .\" Modified Wed Nov 6 03:46:05 1996 by Eric S. Raymond <esr@thyrsus.com> | |
| 29 | .\" | |
| 30 | .TH ALARM 2 1993-07-21 Linux "Linux Programmer's Manual" | |
| 31 | .SH NAME | |
| 32 | alarm \- set an alarm clock for delivery of a signal | |
| 33 | .SH SYNOPSIS | |
| 34 | .nf | |
| 35 | .B #include <unistd.h> | |
| 36 | .sp | |
| 37 | .BI "unsigned int alarm(unsigned int " seconds ); | |
| 38 | .fi | |
| 39 | .SH DESCRIPTION | |
| 40 | .BR alarm " arranges for a " SIGALRM | |
| 41 | signal to be delivered to the process in | |
| 42 | .I seconds | |
| 43 | seconds. | |
| 44 | ||
| 45 | If | |
| 46 | .I seconds | |
| 47 | is zero, no new | |
| 48 | .B alarm | |
| 49 | is scheduled. | |
| 50 | ||
| 51 | In any event any previously set | |
| 52 | .B alarm | |
| 53 | is cancelled. | |
| 54 | .SH "RETURN VALUE" | |
| 55 | .B alarm | |
| 56 | returns the number of seconds remaining until any previously scheduled | |
| 57 | alarm was due to be delivered, or zero if there was no previously | |
| 58 | scheduled alarm. | |
| 59 | .SH NOTES | |
| 60 | .BR alarm " and " setitimer | |
| 61 | share the same timer; calls to one will interfere with use of the | |
| 62 | other. | |
| 63 | .PP | |
| 64 | .B sleep() | |
| 65 | may be implemented using | |
| 66 | .BR SIGALRM ; | |
| 67 | mixing calls to | |
| 68 | .B alarm() | |
| 69 | and | |
| 70 | .B sleep() | |
| 71 | is a bad idea. | |
| 72 | ||
| 73 | Scheduling delays can, as ever, cause the execution of the process to | |
| 74 | be delayed by an arbitrary amount of time. | |
| 75 | .SH "CONFORMING TO" | |
| 76 | SVr4, SVID, POSIX, X/OPEN, BSD 4.3 | |
| 77 | .SH "SEE ALSO" | |
| 78 | .BR gettimeofday (2), | |
| 79 | .BR pause (2), | |
| 80 | .BR select (2), | |
| 81 | .BR setitimer (2), | |
| 82 | .BR sigaction (2), | |
| 83 | .BR signal (2), | |
| 84 | .BR sleep (3) |