ualarm(3) - Linux man page

Name

ualarm - schedule signal after given number of microseconds

Synopsis

/* BSD version */
#include <unistd.h>
unsigned int ualarm(unsigned int usecs, unsigned int interval);
/* SUSv2 version */
#define _XOPEN_SOURCE 500
#include <unistd.h>
useconds_t ualarm(useconds_t usecs, useconds_t interval);

Description

The ualarm() function causes the signal SIGALRM to be sent to the invoking process after (not less than) usecs microseconds. The delay may be lengthened slightly by any system activity or by the time spent processing the call or by the granularity of system timers.

Unless caught or ignored, this signal will terminate the process.

If the interval argument is non-zero, further SIGALRM signals will be sent every interval microseconds after the first.

Return Value

This function returns the number of microseconds remaining from the previous call, or 0 when no alarm is pending.

Errors

EINTR: Interrupted by a signal.
EINVAL: usecs or interval is not smaller than 1000000. (On systems where that is considered an error.)

Conforming to

4.3BSD, POSIX.1-2001. 4.3BSD, SUSv2 and POSIX do not define any errors.

Notes

The type useconds_t is an unsigned integer type capable of holding integers in the range [0,1000000]. This type is defined by <sys/types.h> included by <unistd.h> but glibc defines it only when _XOPEN_SOURCE has a value not less than 500, or both _XOPEN_SOURCE and _XOPEN_SOURCE_EXTENDED are defined. Programs will be more portable if they never mention this type explicitly.

The interaction of this function with other timer functions such as alarm(), sleep(), nanosleep(), setitimer(), timer_create(), timer_delete(), timer_getoverrun(), timer_gettime(), timer_settime(), usleep() is unspecified.

This function is obsolete. Use nanosleep(2) or setitimer(2) instead.