timeradd(3)

✨ timeradd — the timeval glow-up page ✨

okay bestie, welcome to timeradd(3), aka the Library Functions Manual entry for a whole lil squad of macros: timeradd, timersub, timercmp, timerclear, timerisset. they do operations on timeval. that's the whole vibe. 💖

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🌸 NAME 🌸

timeradd, timersub, timercmp, timerclear, timerisset — timeval operations 💅

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🎀 LIBRARY 🎀

Standard C library (libc, -lc)

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✨ SYNOPSIS ✨

#include <sys/time.h>

void timeradd(struct timeval *a, struct timeval *b,
              struct timeval *res);
void timersub(struct timeval *a, struct timeval *b,
              struct timeval *res);

void timerclear(struct timeval *tvp);
int timerisset(struct timeval *tvp);

int timercmp(struct timeval *a, struct timeval *b, CMP);

🧚 Feature Test Macro Requirements for glibc 🧚

(peep feature_test_macros(7) if you wanna go deeper, bestie)

• All functions shown above:
  • Since glibc 2.19:
    • _DEFAULT_SOURCE
  • glibc 2.19 and earlier:
    • _BSD_SOURCE

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💖 DESCRIPTION 💖

so these macros are here to operate on timeval structures, and <sys/time.h> defines them like this:

struct timeval {
    time_t      tv_sec;     /* seconds */
    suseconds_t tv_usec;    /* microseconds */
};

not me obsessing over how clean that is. anyway, one by one:

• timeradd() — adds the time values in a and b, and drops the sum into the timeval pointed to by res. the result gets normalized so that res->tv_usec lands in the range 0 to 999,999. no cap. ✨
• timersub() — subtracts the time value in b from the time value in a, and puts the result in the timeval pointed to by res. also normalized so res->tv_usec is in the range 0 to 999,999. periodt. 🫶
• timerclear() — zeros out the timeval structure pointed to by tvp, so it represents the Epoch: 1970-01-01 00:00:00 +0000 (UTC). it's giving the beginning of time, literally. 💀
• timerisset() — returns true (nonzero) if either field of the timeval structure pointed to by tvp contains a nonzero value. vibe check on your timer. 👑
• timercmp() — compares the timer values in a and b using the comparison operator CMP, and returns true (nonzero) or false (0) depending on how that comparison went.

⚠️ bestie listen. some systems (but not Linux/glibc) have a broken timercmp() implementation where CMP of >=, <=, and == just do not work. tragic. iconic fail. so portable applications can instead use: c !timercmp(..., <) !timercmp(..., >) !timercmp(..., !=)

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🌈 RETURN VALUE 🌈

timerisset() and timercmp() return true (nonzero) or false (0). that's it, that's the tea. 🍓

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💜 ERRORS 💜

No errors are defined. ✨ zero drama, zero errors, we love a low-maintenance function.

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🌟 STANDARDS 🌟

None. 😭 it's just out here living its truth, unstandardized.

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🦋 HISTORY 🦋

BSD. old money, honestly. 👑

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💫 SEE ALSO 💫

• gettimeofday(2)
• time(7)

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and that's the whole page, bestie!! go forth and normalize your microseconds responsibly 💅

signing off — this was Linux man-pages 6.20, dated 2026-02-08, page timeradd(3) 🎀✨