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GETTIMEOFDAY(2) BSD System Calls Manual GETTIMEOFDAY(2) NAME gettimeofday, settimeofday -- get/set date and time SYNOPSIS #include <sys/time.h> int gettimeofday(struct timeval *restrict tp, void *restrict tzp); int settimeofday(const struct timeval *tp, const struct timezone *tzp); DESCRIPTION Note: timezone is no longer used; this information is kept outside the kernel. The system's notion of the current Greenwich time and the current time zone is obtained with the gettimeofday() call, and set with the settimeofday() call. The time is expressed in seconds and microseconds since midnight (0 hour), January 1, 1970. The resolution of the system clock is hardware dependent, and the time may be updated continuously or in ``ticks.'' If tp or tzp is NULL, the associated time information will not be returned or set. The structures pointed to by tp and tzp are defined in <sys/time.h> as: struct timeval { time_t tv_sec; /* seconds since Jan. 1, 1970 */ suseconds_t tv_usec; /* and microseconds */ }; struct timezone { int tz_minuteswest; /* of Greenwich */ int tz_dsttime; /* type of dst correction to apply */ }; The timeval structure specifies a time value in seconds and microseconds. The values in timeval are opaque types whose length may vary on different machines; depending on them to have any given length may lead to errors. The timezone structure indicates the local time zone (measured in minutes of time westward from Greenwich), and a flag that, if nonzero, indicates that Daylight Saving time applies locally during the appropriate part of the year. Only the super-user may set the time of day or time zone. If the system securelevel is greater than 1 (see init(8) ), the time may only be advanced. This limitation is imposed to prevent a malicious super-user from setting arbitrary time stamps on files. The system time can still be adjusted backwards using the adjtime(2) system call even when the sys-tem system tem is secure. RETURN A 0 return value indicates that the call succeeded. A -1 return value indicates an error occurred, and in this case an error code is stored into the global variable errno. ERRORS The following error codes may be set in errno: [EFAULT] An argument address referenced invalid memory. [EPERM] A user other than the super-user attempted to set the time. LEGACY SYNOPSIS #include <sys/time.h> int gettimeofday(struct timeval *tp, struct timezone *tzp); The type of tzp has changed. SEE ALSO date(1), adjtime(2), ctime(3), compat(5), timed(8) HISTORY The gettimeofday() function call appeared in 4.2BSD. 4th Berkeley Distribution May 26, 1995 4th Berkeley Distribution |