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alarm(3) [osf1 man page]

alarm(3)						     Library Functions Manual							  alarm(3)

NAME
alarm, ualarm - Sets or changes the timeout of interval timers. LIBRARY
Standard C Library (libc) SYNOPSIS
#include <unistd.h> unsigned int alarm( unsigned int seconds); useconds_t ualarm( useconds_t useconds, useconds_t interval); STANDARDS
Interfaces documented on this reference page conform to industry standards as follows: alarm(), ualarm(): XSH5.0 Refer to the standards(5) reference page for more information about industry standards and associated tags. PARAMETERS
Specifies a number of real-time seconds. Specifies a number of real-time microseconds. Specifies the interval for repeating the timer. DESCRIPTION
The alarm() function is used to obtain notification of a timeout after the number of real-time seconds specified by the seconds parameter has elapsed. At some time after seconds seconds have elapsed, a signal is delivered to the process. Each call resets the timer to the new value. A value of 0 (zero) disables the timer. When the notification signal is caught or ignored, no action takes place; otherwise the calling process is terminated. The alarm() function uses the ITIMER_REAL interval timer. The ualarm() function is used to obtain notification of a timeout after the number of real-time microseconds specified by the useconds parameter has elapsed. When the interval parameter is nonzero, timeout notification occurs after the number of microseconds specified by the interval parameter has been added to the useconds parameter. When the notification signal is caught or ignored, no action takes place; otherwise the calling process is terminated. The ualarm() function is the simplified interface to the setitimer() function, and uses the ITIMER_REAL interval timer. NOTES
The alarm() and ualarm() functions are supported for multithreaded applications. Although the alarm() and ualarm() functions are reentrant, it should be noted that just as the second of two calls from a single thread to alarm() resets the timer, this is also true if two calls are made from different threads. RETURN VALUES
If there is a previous alarm() request with time remaining, the alarm() function returns a non-zero value that is the number of seconds until the previous request would have generated a SIGALRM signal. Otherwise, alarm() returns 0 (zero). The ualarm() function returns the number of microseconds remaining from the previous ualarm() call. If no timeouts are pending or if ualarm() has not previously been called, ualarm() returns 0 (zero). ERRORS
The alarm() function sets errno to the specified values for the following conditions: [Tru64 UNIX] The seconds parameter specifies a value greater than 100,000,000. RELATED INFORMATION
Functions: gettimer(3) Standards: standards(5) delim off alarm(3)

Check Out this Related Man Page

UALARM(3P)						     POSIX Programmer's Manual							UALARM(3P)

PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the correspond- ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. NAME
ualarm - set the interval timer SYNOPSIS
#include <unistd.h> useconds_t ualarm(useconds_t useconds, useconds_t interval); DESCRIPTION
The ualarm() function shall cause the SIGALRM signal to be generated for the calling process after the number of realtime microseconds specified by the useconds argument has elapsed. When the interval argument is non-zero, repeated timeout notification occurs with a period in microseconds specified by the interval argument. If the notification signal, SIGALRM, is not caught or ignored, the calling process is terminated. Implementations may place limitations on the granularity of timer values. For each interval timer, if the requested timer value requires a finer granularity than the implementation supports, the actual timer value shall be rounded up to the next supported value. Interactions between ualarm() and any of the following are unspecified: alarm() nanosleep() setitimer() timer_create() timer_delete() timer_getoverrun() timer_gettime() timer_settime() sleep() RETURN VALUE
The ualarm() function shall return the number of microseconds remaining from the previous ualarm() call. If no timeouts are pending or if ualarm() has not previously been called, ualarm() shall return 0. ERRORS
No errors are defined. The following sections are informative. EXAMPLES
None. APPLICATION USAGE
Applications are recommended to use nanosleep() if the Timers option is supported, or setitimer(), timer_create(), timer_delete(), timer_getoverrun(), timer_gettime(), or timer_settime() instead of this function. RATIONALE
None. FUTURE DIRECTIONS
None. SEE ALSO
alarm(), nanosleep(), setitimer(), sleep(), timer_create(), timer_delete(), timer_getoverrun(), the Base Definitions volume of IEEE Std 1003.1-2001, <unistd.h> COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol- ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . IEEE
/The Open Group 2003 UALARM(3P)

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