sys_time.h(0P)

🌸 PROLOG 🌸

ok so this page is literally part of the POSIX Programmer's Manual, bestie. quick heads up tho — the Linux implementation of this interface may differ (so pls consult the corresponding Linux manual page for the deets on Linux behavior), or honestly the interface may not even be implemented on Linux at all. 💀

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💖 NAME 💖

sys/time.h — time types, that's it, that's the vibe ✨

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✨ SYNOPSIS ✨

#include <sys/time.h>

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🎀 DESCRIPTION 🎀

okay so the <sys/time.h> header shall define the timeval structure, and it shall include at least these members:

time_t         tv_sec      Seconds.
suseconds_t    tv_usec     Microseconds.

and the <sys/time.h> header shall define the itimerval structure, which shall include at least these members:

struct timeval it_interval Timer interval.
struct timeval it_value    Current value.

the <sys/time.h> header shall define the time_t and suseconds_t types exactly as described in <sys/types.h>. 🫶

the <sys/time.h> header shall define the fd_set type as described in <sys/select.h>.

then the <sys/time.h> header shall define these symbolic constants 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 👑

the <sys/time.h> header shall define the following as described in <sys/select.h>: FD_CLR() FD_ISSET() FD_SET() FD_ZERO() FD_SETSIZE

and the following shall be declared as functions, and may also be defined as macros. function prototypes shall be provided, no cap:

int   getitimer(int, struct itimerval *);
int   gettimeofday(struct timeval *restrict, void *restrict);
int   setitimer(int, const struct itimerval *restrict,
          struct itimerval *restrict);
int   select(int, fd_set *restrict, fd_set *restrict, fd_set *restrict,
          struct timeval *restrict);
int   utimes(const char *, const struct timeval [2]);

lowkey important: inclusion of the <sys/time.h> header may make visible all symbols from the <sys/select.h> header. so yeah. 🙈

the following sections are informative — meaning they're the bonus content, not the graded homework 📚

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🌈 APPLICATION USAGE 🌈

None. literally none. we love a low-effort queen 💅

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🧚 RATIONALE 🧚

None. also none. iconic behavior honestly ✨

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🦋 FUTURE DIRECTIONS 🦋

None. she said "no notes, no changes" 💖

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⭐ SEE ALSO ⭐

• <sys_select.h>, <sys_types.h>
• The System Interfaces volume of POSIX.1‐2017, futimens(), getitimer(), gettimeofday(), pselect()

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👑 COPYRIGHT 👑

portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group.

in the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document — so like, that's the main character, this one's just the vibe. 🫡

the original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. to report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html . 🐛

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and that's the whole page bestie!! brought to you by IEEE/The Open Group, circa 2017, filed under sys_time.h(0P) — stay hydrated, go call gettimeofday(), mwah 💋💖✨