table of contents
other versions
- wheezy 3.44-1
- jessie 3.74-1
- jessie-backports 4.10-2~bpo8+1
- testing 4.10-2
- unstable 4.10-2
other sections
GETTIMEOFDAY(2) | Linux Programmer's Manual | GETTIMEOFDAY(2) |
NAME¶
gettimeofday, settimeofday - get / set timeSYNOPSIS¶
#include <sys/time.h> int gettimeofday(struct timeval *tv, struct timezone *tz); int settimeofday(const struct timeval *tv, const struct timezone *tz);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
DESCRIPTION¶
The functions gettimeofday() and settimeofday() can get and set the time as well as a timezone. The tv argument is a struct timeval (as specified in <sys/time.h>):struct timeval { time_t tv_sec; /* seconds */ suseconds_t tv_usec; /* microseconds */ };
struct timezone { int tz_minuteswest; /* minutes west of Greenwich */ int tz_dsttime; /* type of DST correction */ };
If either tv or tz is NULL, the corresponding structure is not set or returned. (However, compilation warnings will result if tv is NULL.) The use of the timezone structure is obsolete; the tz argument should normally be specified as NULL. (See NOTES below.)
RETURN VALUE¶
gettimeofday() and settimeofday() return 0 for success, or -1 for failure (in which case errno is set appropriately).ERRORS¶
- EFAULT
- One of tv or tz pointed outside the accessible address space.
- EINVAL
- Timezone (or something else) is invalid.
- EPERM
- The calling process has insufficient privilege to call settimeofday(); under Linux the CAP_SYS_TIME capability is required.
CONFORMING TO¶
SVr4, 4.3BSD. POSIX.1-2001 describes gettimeofday() but not settimeofday(). POSIX.1-2008 marks gettimeofday() as obsolete, recommending the use of clock_gettime(2) instead.NOTES¶
The time returned by gettimeofday(2) is affected by discontinuous jumps in the system time (e.g., if the system administrator manually changes the system time). If you need a monotonically increasing clock, see clock_gettime(2).DST_NONE /* not on DST */DST_USA /* USA style DST */DST_AUST /* Australian style DST */DST_WET /* Western European DST */DST_MET /* Middle European DST */DST_EET /* Eastern European DST */DST_CAN /* Canada */DST_GB /* Great Britain and Eire */DST_RUM /* Romania */DST_TUR /* Turkey */DST_AUSTALT /* Australian style with shift in 1986 */
Of course it turned out that the period in which Daylight Saving Time is in force cannot be given by a simple algorithm, one per country; indeed, this period is determined by unpredictable political decisions. So this method of representing timezones has been abandoned.
SEE ALSO¶
date(1), adjtimex(2), clock_gettime(2), time(2), ctime(3), ftime(3), timeradd(3), capabilities(7), time(7)COLOPHON¶
This page is part of release 3.44 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.2012-04-26 | Linux |