![]() The timeval struct used to measure time has only two fields, andīoth are unsigned ints. Ru_nivcsw involuntary context switches (process loses CPU) Ru_nvcsw voluntary context switches (process loses CPU) ![]() Ru_oublock block output operations, disc, etc Ru_inblock block input operations, disc etc Ru_minflt minor page faults: "page reclaims" Ru_isrss stack size (memory used by local variables) Ru_idrss memory size for statics, globals, and new/malloc Ru_maxrss max resident set size (physical memory allocated) Ru_stime time spent executing system functions (the first two fields are structs of type timeval, see below) The fields of this struct are as follows: Program must create, and which will be filled in with statistics on The results parameter is a pointer to a struct that the calling Unix provides no useful way to obtain information for Process, RUSAGE_CHILDREN measures only subprocesses that have already The target parameter must be one of the two pre-defined values Returns 0 for success, and negative for failure there are no reasonable Int getrusage(int target, rusage * results) include: include: Note: this function is available under DOS and Windows, but the moreĪccurate version, getrusage is unix only. The clock function provides a very simple interface, butĭoes not distinguish between time spent on user code and time spentĮxecuting system functions it merely measures the total CPU timeĭevoted so far to the current process. Printf("%.4lf seconds of processing\n", (t2-t1)/(double)CLOCKS_PER_SEC) Process, measured in units of CLOCKS_PER_SEC, which on this system Returns the amount of processor time actually used by the current Values using the %u format, and everything. Int values to a time_t variable, and vice-versa, and print time_t Is exactly identical to "unsigned int" in behaviour. The second parameter (NULL) used to be to retrieve the local time zone,īut time zones are no-longer handled that way. Printf("%.6lf seconds elapsed\n", t2-t1) Don't be fooled: although the units are microseconds, the value The other (called tv_usec) is the number of microseconds into that Would be returned by time, the time in seconds since. One (called tv_sec) is exactly the value that The parameter must be a pointer to a previouslyĭeclared timeval variable (or in C, a struct timeval variable). Int gettimeofday(timeval *tp, NULL) include: Note In C programs (as opposed to C++) the word "struct" must Of ctime uses the same array, so the results of any call are alwaysĬtime_r is exactly the same as ctime, except that the caller must provideĪn array of chars big enough to hold the result. Warning the char* string returned is a static array, every call Newline character, which usually has to be removed. The date is always absurdly followed by a The value returned may be used as a reliable measure of elapsed time,Īnd may be passed to ctime() for conversion into a human-readableĬhar *ctime(time_t *ptr) char *ctime_r(time_t *ptr, char *output) include: Note that the parameter must be a pointer to the numeric time.Ĭonverts the time provided into a human-readable string, the formatĭates are padded with a space if only one digit long, and time componentsĪre given leading zeros. Is not NULL, the same value is stored in the location pointed to.įollow this link for information on the time_t type. January 1970 GMT (or 7pm, 31st December 1969 EST). Returns the number of seconds that have passed since midnight, 1st Time_t time(void) time_t time(time_t *ptr) include: Time_t values are converted to readable strings by ctime. Time_t values are analysed into y,m,d,h,m,s by localtime and gmtime. Time_t values are produced from y,m,d,h,m,s parts by mktime and timegm. Time_t values are produced from the clock by time. Monday 18th January 2038, which will appear to be 3:45:52pm on Friday Otherwise unix will have its own "Y2K" problem at 10:14:08pm on The meaning of "int" will change from 4-byte-integer to 8-byte-integer, In the future, either time_t will cease to be identical to int, or To a time_t variable, and vice-versa, and print time_t values using Is exactly identical to "int" in behaviour. Timegm Converts d,m,y,h,m,s parts into seconds GMT. Mktime Converts d,m,y,h,m,s parts into seconds. Gettimeofday Get actual time, resolution 0.01 seconds. Gmtime Split time (seconds) into d,m,y,h,m,s GMT. Localtime Split time (seconds) into d,m,y,h,m,s. ![]() Tm Explanation of tm type for d,m,y,h,m,s. Time Get actual time, resolution 1 second.Ĭtime Convert time (seconds) to printable string. Time_t Explanation of type for simple times. Unix, C, and C++ Function Reference Unix, C, and C++Ĭlock_t Explanation of type for CPU times.
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