Return to getitimer.2 CVS log

Up to [CSRG BSD Unix] / 43BSDTahoe / man / man2

Annotation of 43BSDTahoe/man/man2/getitimer.2, revision 1.1.1.1

1.1       root        1: .\" Copyright (c) 1983 Regents of the University of California.
                      2: .\" All rights reserved.  The Berkeley software License Agreement
                      3: .\" specifies the terms and conditions for redistribution.
                      4: .\"
                      5: .\"    @(#)getitimer.2 6.3 (Berkeley) 12/18/86
                      6: .\"
                      7: .TH GETITIMER 2 "December 18, 1986"
                      8: .UC 5
                      9: .SH NAME
                     10: getitimer, setitimer \- get/set value of interval timer
                     11: .SH SYNOPSIS
                     12: .nf
                     13: .ft B
                     14: #include <sys/time.h>
                     15: .PP
                     16: .ft B
                     17: #define ITIMER_REAL    0       /* real time intervals */
                     18: #define ITIMER_VIRTUAL 1       /* virtual time intervals */
                     19: #define ITIMER_PROF    2       /* user and system virtual time */
                     20: .sp
                     21: .ft B
                     22: getitimer(which, value)
                     23: int which;
                     24: struct itimerval *value;
                     25: .PP
                     26: .ft B
                     27: setitimer(which, value, ovalue)
                     28: int which;
                     29: struct itimerval *value, *ovalue;
                     30: .fi
                     31: .SH DESCRIPTION
                     32: The system provides each process with three interval timers,
                     33: defined in
                     34: .RI < sys/time.h >.
                     35: The
                     36: .I getitimer
                     37: call returns the current value for the timer specified in
                     38: .I which
                     39: in the structure at
                     40: .IR value .
                     41: The
                     42: .I setitimer
                     43: call sets a timer to the specified
                     44: .I value
                     45: (returning the previous value of the timer if
                     46: .I ovalue
                     47: is nonzero).
                     48: .PP
                     49: A timer value is defined by the 
                     50: .I itimerval
                     51: structure:
                     52: .PP
                     53: .nf
                     54: .RS
                     55: .DT
                     56: struct itimerval {
                     57:        struct  timeval it_interval;    /* timer interval */
                     58:        struct  timeval it_value;       /* current value */
                     59: };
                     60: .RE
                     61: .fi
                     62: .PP
                     63: If
                     64: .I it_value
                     65: is non-zero, it indicates the time to the next timer expiration. 
                     66: If
                     67: .I it_interval
                     68: is non-zero, it specifies a value to be used in reloading 
                     69: .I it_value
                     70: when the timer expires.
                     71: Setting 
                     72: .I it_value
                     73: to 0 disables a timer.  Setting 
                     74: .I it_interval
                     75: to 0 causes a timer to be disabled after its next expiration (assuming
                     76: .I it_value
                     77: is non-zero).
                     78: .PP
                     79: Time values smaller than the resolution of the
                     80: system clock are rounded up to this resolution
                     81: (on the VAX, 10 milliseconds).
                     82: .PP
                     83: The ITIMER_REAL timer decrements in real time.  A SIGALRM signal is
                     84: delivered when this timer expires.
                     85: .PP
                     86: The ITIMER_VIRTUAL timer decrements in process virtual time.
                     87: It runs only when the process is executing.  A SIGVTALRM signal
                     88: is delivered when it expires.
                     89: .PP
                     90: The ITIMER_PROF timer decrements both in process virtual time and
                     91: when the system is running on behalf of the process.  It is designed
                     92: to be used by interpreters in statistically profiling the execution
                     93: of interpreted programs.
                     94: Each time the ITIMER_PROF timer expires, the SIGPROF signal is
                     95: delivered.  Because this signal may interrupt in-progress
                     96: system calls, programs using this timer must be prepared to
                     97: restart interrupted system calls.
                     98: .SH NOTES
                     99: Three macros for manipulating time values are defined in
                    100: .RI < sys/time.h >.
                    101: .I Timerclear
                    102: sets a time value to zero,
                    103: .I timerisset
                    104: tests if a time value is non-zero, and
                    105: .I timercmp
                    106: compares two time values (beware that >= and <= do not
                    107: work with this macro).
                    108: .SH "RETURN VALUE
                    109: If the calls succeed, a value of 0 is returned.  If an error occurs,
                    110: the value \-1 is returned, and a more precise error code is placed
                    111: in the global variable \fIerrno\fP.
                    112: .SH "ERRORS
                    113: The possible errors are:
                    114: .TP 15
                    115: [EFAULT]
                    116: The \fIvalue\fP parameter specified a bad address.
                    117: .TP 15
                    118: [EINVAL]
                    119: A \fIvalue\fP parameter specified a time was too large
                    120: to be handled.
                    121: .SH "SEE ALSO"
                    122: select(2), sigvec(2), gettimeofday(2)

This archive runs on limited infrastructure. Preserving old code on modern bandwidth. Automated agents are requested to crawl responsibly.