rtc(1m) [netbsd man page]
rtc(1M) System Administration Commands rtc(1M) NAME
rtc - provide all real-time clock and GMT-lag management SYNOPSIS
/usr/sbin/rtc [-c] [-z zone-name] DESCRIPTION
On x86 systems, the rtc command reconciles the difference in the way that time is established between UNIX and MS-DOS systems. UNIX systems utilize Greenwich Mean Time (GMT), while MS-DOS systems utilize local time. Without arguments, rtc displays the currently configured time zone string. The currently configured time zone string is based on what was last recorded by rtc-z zone-name. The rtc command is not normally run from a shell prompt; it is generally invoked by the system. Commands such as date(1) and rdate(1M), which are used to set the time on a system, invoke /usr/sbin/rtc -c to ensure that daylight savings time (DST) is corrected for properly. OPTIONS
-c This option checks for DST and makes corrections if necessary. It is normally run once a day by a cron job. If there is no RTC time zone or /etc/rtc_config file, this option will do nothing. -z zone-name This option, which is normally run by the system at software installation time, is used to specify the time zone in which the RTC is to be maintained. It updates the configuration file /etc/rtc_config with the name of the specified zone and the current GMT lag for that zone. If there is an existing rtc_config file, this command will update it. If not, this command will create it. FILES
/etc/rtc_config The data file used to record the time zone and GMT lag. This file is completely managed by /usr/sbin/rtc, and it is read by the kernel. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Architecture |x86 | +-----------------------------+-----------------------------+ |Availability |SUNWcsu | +-----------------------------+-----------------------------+ SEE ALSO
date(1), rdate(1M), attributes(5) SunOS 5.10 3 Oct 2003 rtc(1M)
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CTIME(2) System Calls Manual CTIME(2) NAME
ctime, localtime, gmtime, asctime, timezone - convert date and time to ASCII SYNOPSIS
#include <u.h> #include <libc.h> char* ctime(long clock) Tm* localtime(long clock) Tm* gmtime(long clock) char* asctime(Tm *tm) /env/timezone DESCRIPTION
Ctime converts a time clock such as returned by time(2) into ASCII (sic) and returns a pointer to a 30-byte string in the following form. All the fields have constant width. Wed Aug 5 01:07:47 EST 1973 Localtime and gmtime return pointers to structures containing the broken-down time. Localtime corrects for the time zone and possible day- light savings time; gmtime converts directly to GMT. Asctime converts a broken-down time to ASCII and returns a pointer to a 30-byte string. typedef struct { int sec; /* seconds (range 0..59) */ int min; /* minutes (0..59) */ int hour; /* hours (0..23) */ int mday; /* day of the month (1..31) */ int mon; /* month of the year (0..11) */ int year; /* year A.D. - 1900 */ int wday; /* day of week (0..6, Sunday = 0) */ int yday; /* day of year (0..365) */ char zone[4]; /* time zone name */ } Tm; When local time is first requested, the program consults the timezone environment variable to determine the time zone and converts accord- ingly. (This variable is set at system boot time by init(8).) The timezone variable contains the normal time zone name and its difference from GMT in seconds followed by an alternate (daylight) time zone name and its difference followed by a newline. The remainder is a list of pairs of times (seconds past the start of 1970, in the first time zone) when the alternate time zone applies. For example: EST -18000 EDT -14400 9943200 25664400 41392800 57718800 ... Greenwich Mean Time is represented by GMT 0 SOURCE
/sys/src/libc/9sys SEE ALSO
date(1), time(2), init(8) BUGS
The return values point to static data whose content is overwritten by each call. Daylight Savings Time is ``normal'' in the Southern hemisphere. These routines are not equipped to handle non-ASCII text, and are provincial anyway. CTIME(2)