ctime.3

UNIX v6源代码 这几乎是最经典的unix版本 unix操作系统设计和莱昂氏unix源代码分析都是用的该版

.th CTIME III 10/15/73
.sh NAME
ctime, localtime, gmtime  \*-  convert date and time to ASCII
.sh SYNOPSIS
.ft B
char *ctime(tvec)
.br
int tvec[2];
.s3
.ft R
[from Fortran]
.br
.ft B
double precision ctime
.br
.li
... = ctime(dummy)
.s3
int *localtime(tvec)
.br
int tvec[2];
.s3
int *gmtime(tvec)
.br
int tvec[2];
.br
.ft R
.sh DESCRIPTION
.it Ctime
converts a time in the vector
.it tvec
such as returned by time (II)
into ASCII
and returns a pointer to a
character string
in the form
.s3
    Sun Sep 16 01:03:52 1973\\n\\0
.s3
All the fields have constant width.
.s3
The
.it localtime
and
.it gmtime
entries return pointers to integer vectors containing
the broken-down time.
.it Localtime
corrects for the time zone and possible daylight savings time;
.it gmtime
converts directly to GMT, which is the time UNIX uses.
The value is a pointer
to an array whose components are
.s3
.lp +5 5
0	seconds
.lp +5 5
1	minutes
.lp +5 5
2	hours
.lp +5 5
3	day of the month (1-31)
.lp +5 5
4	month (0-11)
.lp +5 5
5	year \*- 1900
.lp +5 5
6	day of the week (Sunday = 0)
.lp +5 5
7	day of the year (0-365)
.lp +5 5
8	Daylight Saving Time flag if non-zero
.i0
.s3
The external variable
.it timezone
contains the difference, in seconds, between GMT and local
standard time (in EST, is 5*60*60);
the external variable
.it daylight
is non-zero iff the standard U.S.A. Daylight
Savings Time conversion should be applied.
The program knows about the peculiarities
of this conversion in 1974 and 1975;
if necessary,
a table for these years can be extended.
.s3
A routine named
.it ctime
is also available from Fortran.
Actually it more resembles the
.it time
(II) system entry in that it returns the number of seconds
since the epoch
0000 GMT Jan. 1, 1970
(as a floating-point number).
.sh "SEE ALSO"
time(II)
.sh BUGS