SYSTIME.H(7) Miscellaneous Information Manual SYSTIME.H(7)

NAME

sys/time.h — time types

SYNOPSIS

#include <sys/time.h>

DESCRIPTION

The <sys/time.h> header defines the timeval structure that includes at least the following members:

time_t         tv_sec      seconds
suseconds_t    tv_usec     microseconds

The <sys/time.h> header defines the itimerval structure that includes at least the following members: struct timeval it_interval timer interval struct timeval it_value current value

The time_t and suseconds_t types are defined as described in <sys/types.h>.

The <sys/time.h> header defines the fd_set type as a structure that includes at least the following member: long fds_bits[] bit mask for open file descriptions

The <sys/time.h> header defines the following values for the which argument of getitimer() and setitimer():

ITIMER_REAL: Decrements in real time.
ITIMER_VIRTUAL: Decrements in process virtual time.
ITIMER_PROF: Decrements both in process virtual time and when the system is running on behalf of the process.

Each of the following may be declared as a function, or defined as a macro, or both:

void FD_CLR(int fd, fd_set *fdset): Clears the bit for the file descriptor fd in the file descriptor set fdset .
int FD_ISSET(int fd, fd_set *fdset): Returns a non-zero value if the bit for the file descriptor fd is set in the file descriptor set by fdset , and 0 otherwise.
void FD_SET(int fd, fd_set *fdset): Sets the bit for the file descriptor fd in the file descriptor set fdset .
void FD_ZERO(fd_set *fdset): Initialises the file descriptor set fdset to have zero bits for all file descriptors.
FD_SETSIZE: Maximum number of file descriptors in an fd_set structure.

If implemented as macros, these may evaluate their arguments more than once, so that arguments must never be expressions with side effects.

The following are declared as functions and may also be defined as macros. Function prototypes must be provided for use with an ISO C compiler. int getitimer(int, struct itimerval *); int setitimer(int, const struct itimerval *, struct itimerval *); int gettimeofday(struct timeval *, void *); int select(int, fd_set *, fd_set *, fd_set *, struct timeval *); int utimes(const char *, const struct timeval [2]);

APPLICATION USAGE

None.

FUTURE DIRECTIONS