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@(#)gettimeofday.2 8.2 (Berkeley) 5/26/95
.Dd August 5, 2008 .Dt GETTIMEOFDAY 2 .Os BSD 4 .Sh NAME .Nm gettimeofday , .Nm settimeofday .Nd get/set date and time .Sh SYNOPSIS .Fd #include <sys/time.h> .Ft int .Fo gettimeofday .Fa "struct timeval *restrict tp" .Fa "void *restrict tzp" .Fc .Ft int .Fo settimeofday .Fa "const struct timeval *tp" .Fa "const struct timezone *tzp" .Fc .Sh DESCRIPTION
p The system's notion of the current Greenwich time and the current time zone is obtained with the .Fn gettimeofday call, and set with the .Fn 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 .Fa tp is NULL and .Fa tzp is non-NULL, .Fn gettimeofday will populate the timezone struct in .Fa tzp . If .Fa tp is non-NULL and .Fa tzp is NULL, then only the timeval struct in .Fa tp is populated. If both .Fa tp and .Fa tzp are NULL, nothing is returned.
p The structures pointed to by .Fa tp and .Fa tzp are defined in .Ao Pa sys/time.h Ac as:
p d -literal 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 */ }; .Ed
p The .Fa timeval structure specifies a time value in seconds and microseconds. The values in .Fa timeval are opaque types whose length may vary on different machines; depending on them to have any given length may lead to errors.
p The .Fa 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.
p Only the super-user may set the time of day or time zone. If the system securelevel is greater than 1 (see .Xr 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 .Xr adjtime 2 system call even when the system is secure. .Sh 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 .Va errno . .Sh ERRORS The following error codes may be set in .Va errno : l -tag -width [EFAULT] t Bq Er EFAULT An argument address referenced invalid memory. t Bq Er EPERM A user other than the super-user attempted to set the time. .El .Sh LEGACY SYNOPSIS .Fd #include <sys/time.h>
p .Ft int
.Fo gettimeofday .Fa "struct timeval *tp" .Fa "struct timezone *tzp" .Fc ;
p The type of .Fa tzp has changed. .Sh SEE ALSO .Xr date 1 , .Xr adjtime 2 , .Xr ctime 3 , .Xr compat 5 , .Xr timed 8 .Sh HISTORY The .Fn gettimeofday function call appeared in x 4.2 .