time() C99 compliance:

[dragonfly.git] / lib / libc / gen / time.3

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.\"     @(#)time.3	8.1 (Berkeley) 6/4/93
.\" $FreeBSD: src/lib/libc/gen/time.3,v 1.15 2007/01/09 00:27:55 imp Exp $
.\" $DragonFly: src/lib/libc/gen/time.3,v 1.2 2003/06/17 04:26:42 dillon Exp $
.\"
.Dd July 18, 2003
.Dt TIME 3
.Os
.Sh NAME
.Nm time
.Nd get time of day
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In time.h
.Ft time_t
.Fn time "time_t *tloc"
.Sh DESCRIPTION
The
.Fn time
function
returns the value of time in seconds since 0 hours, 0 minutes,
0 seconds, January 1, 1970, Coordinated Universal Time.
If an error occurs,
.Fn time
returns the value
.Po Vt time_t Pc Ns \-1 .
.Pp
The return value is also stored in
.No \&* Ns Va tloc ,
provided that
.Va tloc
is non-null.
.Sh ERRORS
The
.Fn time
function may fail for any of the reasons described in
.Xr gettimeofday 2 .
.Sh SEE ALSO
.Xr gettimeofday 2 ,
.Xr ctime 3
.Sh STANDARDS
The
.Nm
function conforms to
.St -p1003.1-2001 .
.Sh HISTORY
A
.Fn time
function appeared in
.At v6 .
.Sh BUGS
Neither
.St -isoC-99
nor
.St -p1003.1-2001
requires
.Fn time
to set
.Va errno
on failure; thus, it is impossible for an application to distinguish
the valid time value \-1 (representing the last UTC second of 1969)
from the error return value.
.Pp
Systems conforming to earlier versions of the C and
.Tn POSIX
standards (including older versions of
.Fx )
did not set
.No \&* Ns Va tloc
in the error case.