times(2)

Purpose

times() stores the CPU time accounting of the calling process into struct tms: user and system time of the process itself (tms_utime, tms_stime) and of all waited-for terminated children (tms_cutime, tms_cstime) (times.2, DESCRIPTION). The return value is the uptime in clock ticks – a monotonic anchor that lets callers turn two samples into elapsed wall time.

Synopsis

#include <sys/times.h>
clock_t times(struct tms *buf);

Arguments and behavior

buf receives the four accounting fields (times.2, DESCRIPTION, struct tms). Children’s times fold in only after wait(2)-style reaping (the “waited-for terminated” wording; see wait4). The tick unit comes from sysconf(_SC_CLK_TCK) – nominally 100, not CLOCKS_PER_SEC (times.2, NOTES; clock(3) uses a different unit with the same clock_t type, a classic confusion). buf may be NULL to fetch only the uptime return value (kernel convention; the man page documents the struct fill as the purpose).

Return value and errors

Returns the elapsed real time in clock ticks since an arbitrary point (boot); -1 on error with errno set (times.2, RETURN VALUE). Errors: EFAULT (buf invalid). BUGS note: on i386 there is a small window (~41 seconds) after boot where times() can return -1 falsely, and the same false -1 can occur when the tick counter wraps the 32-bit clock_t (times.2, BUGS) – the reason long-lived systems sample uptime via clock_gettime(CLOCK_BOOTTIME) instead.

Flags and constants

None (units from sysconf(_SC_CLK_TCK)).

Security and notes

No capability involved; the accounting shown is the same data getrusage(2) exposes with finer granularity (see getrusage). POSIX requires tms_cutime/tms_cstime to include only reaped children, which is why a still-running child’s CPU time never appears. For benchmarking, prefer clock_gettime(CLOCK_PROCESS_CPUTIME_ID); times() remains the portable-and-cheap coarse probe. Cross-reference: getrusage, wait4, time, sysinfo.

References

• https://man7.org/linux/man-pages/man2/times.2.html
• worklog: wrapper symbol times W @@GLIBC_2.2.5 verified with nm -D against glibc 2.41 (2026-10-17)