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GETTIMEOFDAY(2) BSD System Calls Manual GETTIMEOFDAY(2) NAME gettimeofday, settimeofday -- get/set date and time LIBRARY Standard C Library (libc, -lc) SYNOPSIS #include <sys/time.h> int gettimeofday(struct timeval *tp, struct timezone *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() system call, and set with the settimeofday() system call. The time is expressed in seconds and mi- croseconds since midnight (0 hour), January 1, 1970. The resolution of the system clock is hardware dependent, and the time may be updated con- tinuously or in "ticks". If tp or tzp is NULL, the associated time in- formation 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 */ suseconds_t tv_usec; /* and microseconds */ }; struct timezone { int tz_minuteswest; /* minutes west of Greenwich */ int tz_dsttime; /* type of dst correction */ }; 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 is running at securelevel >= 2 (see init(8)), the time may only be ad- vanced or retarded by a maximum of one second. This limitation is im- posed to prevent a malicious super-user from setting arbitrary time stamps on files. The system time can be adjusted backwards without re- striction using the adjtime(2) system call even when the system is se- cure. RETURN VALUES Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error. 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. SEE ALSO date(1), adjtime(2), clock_gettime(2), ctime(3), timeradd(3), clocks(7), timed(8) HISTORY The gettimeofday() system call appeared in 4.2BSD. BSD May 26, 1995 BSD
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | HISTORY
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