projects / thirdparty / man-pages.git / blame
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1 | .\" This manpage is Copyright (C) 1992 Drew Eckhardt; |
| 2 | .\" 1993 Michael Haardt, Ian Jackson. | |
| 3 | .\" | |
| 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| 14 | .\" manual page may be incorrect or out-of-date.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. | |
| 23 | .\" | |
| 24 | .\" Modified Wed Jul 21 19:42:57 1993 by Rik Faith <faith@cs.unc.edu> | |
| 25 | .\" Modified Sun Jul 21 21:25:26 1996 by Andries Brouwer <aeb@cwi.nl> | |
| 26 | .\" Modified Wed Nov 6 03:46:05 1996 by Eric S. Raymond <esr@thyrsus.com> | |
| 27 | .\" | |
| ffe84477 | 28 | .TH ALARM 2 2008-06-12 "Linux" "Linux Programmer's Manual" |
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29 | .SH NAME |
| 30 | alarm \- set an alarm clock for delivery of a signal | |
| 31 | .SH SYNOPSIS | |
| 32 | .nf | |
| 33 | .B #include <unistd.h> | |
| 34 | .sp | |
| 35 | .BI "unsigned int alarm(unsigned int " seconds ); | |
| 36 | .fi | |
| 37 | .SH DESCRIPTION | |
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38 | .BR alarm () |
| 39 | arranges for a | |
| ae050d9a | 40 | .B SIGALRM |
| ffe84477 | 41 | signal to be delivered to the calling process in |
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42 | .I seconds |
| 43 | seconds. | |
| 44 | ||
| 45 | If | |
| 46 | .I seconds | |
| 47 | is zero, no new | |
| e511ffb6 | 48 | .BR alarm () |
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49 | is scheduled. |
| 50 | ||
| 51 | In any event any previously set | |
| e511ffb6 | 52 | .BR alarm () |
| d9bfdb9c | 53 | is canceled. |
| 47297adb | 54 | .SH RETURN VALUE |
| e511ffb6 | 55 | .BR alarm () |
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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. | |
| 47297adb | 59 | .SH CONFORMING TO |
| 44a2c328 | 60 | SVr4, POSIX.1-2001, 4.3BSD. |
| fea681da | 61 | .SH NOTES |
| ae050d9a | 62 | .BR alarm () |
| c13182ef | 63 | and |
| 0bfa087b | 64 | .BR setitimer (2) |
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65 | share the same timer; calls to one will interfere with use of the |
| 66 | other. | |
| 67 | .PP | |
| 0bfa087b | 68 | .BR sleep (3) |
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69 | may be implemented using |
| 70 | .BR SIGALRM ; | |
| 71 | mixing calls to | |
| 63aa9df0 | 72 | .BR alarm () |
| fea681da | 73 | and |
| 0bfa087b | 74 | .BR sleep (3) |
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75 | is a bad idea. |
| 76 | ||
| 77 | Scheduling delays can, as ever, cause the execution of the process to | |
| 78 | be delayed by an arbitrary amount of time. | |
| 47297adb | 79 | .SH SEE ALSO |
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80 | .BR gettimeofday (2), |
| 81 | .BR pause (2), | |
| 82 | .BR select (2), | |
| 83 | .BR setitimer (2), | |
| 84 | .BR sigaction (2), | |
| 85 | .BR signal (2), | |
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86 | .BR sleep (3), |
| 87 | .BR time (7) |