NAME

time — get time of day

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <time.h>

time_t
time(time_t *tloc);

DESCRIPTION

The time() function returns the value of time in seconds since 0 hours, 0 minutes, 0 seconds, January 1, 1970, Coordinated Universal Time.

A copy of the time value may be saved to the area indicated by the pointer tloc. If tloc is a NULL pointer, no value is stored.

Upon successful completion, time() returns the value of time. Otherwise a value of ((time_t) -1) is returned and the global variable errno is set to indicate the error.

ERRORS

No errors are defined.

SEE ALSO

gettimeofday(2), ctime(3)

STANDARDS

The time() function conforms to IEEE Std 1003.1-1990 (“POSIX.1”).

HISTORY

A time() function appeared in Version 2 AT&T UNIX. It returned a 32-bit value measuring sixtieths of a second, leading to rollover every 2.26 years. In Version 6 AT&T UNIX, the precision of time() was changed to seconds, allowing 135.6 years between rollovers.

In NetBSD 6.0 the time_t type was changed to be 64 bits wide, including on 32-bit machines, making rollover a concern for the far distant future only. Note however that any code making the incorrect assumption that time_t is the same as long will fail on 32-bit machines in 2038.