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Annotation of cci/usr/src/man/man2/getitimer.2, revision 1.1.1.1

1.1       root        1: .TH GETITIMER 2 "27 July 1983"
                      2: .UC 4
                      3: .SH NAME
                      4: getitimer, setitimer \- get/set value of interval timer
                      5: .SH SYNOPSIS
                      6: .nf
                      7: .ft B
                      8: #include <sys/time.h>
                      9: .PP
                     10: .ft B
                     11: #define ITIMER_REAL    0       /* real time intervals */
                     12: #define ITIMER_VIRTUAL 1       /* virtual time intervals */
                     13: #define ITIMER_PROF    2       /* user and system virtual time */
                     14: .sp
                     15: .ft B
                     16: getitimer(which, value)
                     17: int which;
                     18: struct itimerval *value;
                     19: .PP
                     20: .ft B
                     21: setitimer(which, value, ovalue)
                     22: int which;
                     23: struct itimerval *value, *ovalue;
                     24: .fi
                     25: .SH DESCRIPTION
                     26: The system provides each process with three interval timers,
                     27: defined in
                     28: .RI < sys/time.h >.
                     29: The
                     30: .I getitimer
                     31: call returns the current value for the timer specified in
                     32: .IR which ,
                     33: while the
                     34: .I setitimer
                     35: call sets the value of a timer (optionally returning the previous
                     36: value of the timer).
                     37: .PP
                     38: A timer value is defined by the 
                     39: .I itimerval
                     40: structure:
                     41: .PP
                     42: .nf
                     43: .RS
                     44: .DT
                     45: struct itimerval {
                     46:        struct  timeval it_interval;    /* timer interval */
                     47:        struct  timeval it_value;       /* current value */
                     48: };
                     49: .RE
                     50: .fi
                     51: .PP
                     52: If
                     53: .I it_value
                     54: is non-zero, it indicates the time to the next timer expiration. 
                     55: If
                     56: .I it_interval
                     57: is non-zero, it specifies a value to be used in reloading 
                     58: .I it_value
                     59: when the timer expires.
                     60: Setting 
                     61: .I it_value
                     62: to 0 disables a timer.  Setting 
                     63: .I it_interval
                     64: to 0 causes a timer to be disabled after its next expiration (assuming
                     65: .I it_value
                     66: is non-zero).
                     67: .PP
                     68: Time values smaller than the resolution of the
                     69: system clock are rounded up to this resolution
                     70: .PP
                     71: The ITIMER_REAL timer decrements in real time.  A SIGALRM signal is
                     72: delivered when this timer expires.
                     73: .PP
                     74: The ITIMER_VIRTUAL timer decrements in process virtual time.
                     75: It runs only when the process is executing.  A SIGVTALRM signal
                     76: is delivered when it expires.
                     77: .PP
                     78: The ITIMER_PROF timer decrements both in process virtual time and
                     79: when the system is running on behalf of the process.  It is designed
                     80: to be used by interpreters in statistically profiling the execution
                     81: of interpreted programs.
                     82: Each time the ITIMER_PROF timer expires, the SIGPROF signal is
                     83: delivered.  Because this signal may interrupt in-progress
                     84: system calls, programs using this timer must be prepared to
                     85: restart interrupted system calls.
                     86: .SH NOTES
                     87: Three macros for manipulating time values are defined in
                     88: .RI < sys/time.h >.
                     89: .I Timerclear
                     90: sets a time value to zero,
                     91: .I timerisset
                     92: tests if a time value is non-zero, and
                     93: .I timercmp
                     94: compares two time values (beware that >= and <= do not
                     95: work with this macro).
                     96: .SH "RETURN VALUE
                     97: If the calls succeed, a value of 0 is returned.  If an error occurs,
                     98: the value \-1 is returned, and a more precise error code is placed
                     99: in the global variable \fIerrno\fP.
                    100: .SH "ERRORS
                    101: The possible errors are:
                    102: .TP 15
                    103: [EFAULT]
                    104: The \fIvalue\fP structure specified a bad address.
                    105: .TP 15
                    106: [EINVAL]
                    107: A \fIvalue\fP structure specified a time was too large
                    108: to be handled.
                    109: .SH "SEE ALSO"
                    110: sigvec(2), gettimeofday(2)

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