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.Dd April 28, 2024 .Dt GETTIMEOFDAY 2 .Os .Sh NAME .Nm gettimeofday , .Nm settimeofday .Nd get/set date and time .Sh LIBRARY .Lb libc .Sh SYNOPSIS n sys/time.h .Ft int .Fn gettimeofday "struct timeval *tp" "struct timezone *tzp" .Ft int .Fn settimeofday "const struct timeval *tp" "const struct timezone *tzp" .Sh DESCRIPTION .Em Note : The .Nm gettimeofday function
o but not .Nm settimeofday Pc is obsolescent. See the .Sx STANDARDS section for more details.
p The system's notion of the current Greenwich time and the current time zone is obtained with the .Fn gettimeofday system call, and set with the .Fn settimeofday system 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 .Dq ticks . If .Fa tp or .Fa tzp is NULL, the associated time information will not be returned or set.
p The structures pointed to by .Fa tp and .Fa tzp are defined in n sys/time.h as: d -literal 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 */ }; .Ed
p The .Vt 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. The kernel generally does not track these values and they are usually returned as zero. Use .Xr localtime 3 to find the offset for the currently active timezone.
p
Only the super-user may set the time of day or time zone.
If the system is running at securelevel >= 2 (see
.Xr init 8 ) ,
the time may only be advanced or retarded by a maximum of one second.
This limitation is imposed to prevent a malicious super-user
from setting arbitrary time stamps on files.
The system time can be adjusted backwards without restriction using the
.Xr adjtime 2
system call even when the system is secure.
.Sh RETURN VALUES
.Rv -std
.Sh ERRORS
The following error codes may be set in
.Va errno :
l -tag -width Er t Bq Er EINVAL The supplied
.Fa timeval
value is invalid.
t Bq Er EPERM A user other than the super-user attempted to set the time.
.El
.Sh SEE ALSO
.Xr date 1 ,
.Xr adjtime 2 ,
.Xr clock_gettime 2 ,
.Xr ctime 3 ,
.Xr timeradd 3 ,
.Xr clocks 7
.Sh STANDARDS
The
.Nm gettimeofday
function is considered obsolescent and its usage discouraged by
XXX: This should be replaced in the future when an appropriate argument to
the St macro is available: -p1003.1-2017
.No IEEE Std 1003.1-2008, 2017 Edition (\\(LqPOSIX.1\\(Rq) .
Applications should use the
.Xr clock_gettime 2
function instead.
.Sh HISTORY
The
.Fn gettimeofday
system call appeared in
x 4.2 .