[From http://man7.org/linux/man-pages/man1/time.1.html and http://man7.org/linux/man-pages/man2/times.2.html]
---------------------------------------------------------------------------
(i) the elapsed real time between invocation and termination,
(ii) the user CPU time (the sum of the tms_utime and tms_cutime values in a struct tms as returned by times(2))
(iii) the system CPU time (the sum of the tms_stime and tms_cstime values in a struct tms as returned by times(2)).
real = Elapsed real (wall clock) time
user = tms_utime + tms_cutime
sys = tms_stime + tms_cstime
struct tms {
clock_t tms_utime; /* user time */
clock_t tms_stime; /* system time */
clock_t tms_cutime; /* user time of children */
clock_t tms_cstime; /* system time of children */
};
---------------------------------------------------------------------------
[From Ubuntu "$ man time"]
---------------------------------------------------------------------------
real %e
user %U
sys %S
The resource specifiers, which are a superset of those recognized by the tcsh(1) builtin `time' command, are:
% A literal `%'.
E Elapsed real (wall clock) time used by the process, in [hours:]minutes:seconds.
P Percentage of the CPU that this job got. This is just user + system times divided by the total running time. It also prints a percentage sign.
S Total number of CPU-seconds used by the system on behalf of the process (in kernel mode), in seconds.
U Total number of CPU-seconds that the process used directly (in user mode), in seconds.
e Elapsed real (wall clock) time used by the process, in seconds.
---------------------------------------------------------------------------
References:
http://stackoverflow.com/questions/556405/what-do-real-user-and-sys-mean-in-the-output-of-time1
http://blog.he96.com/2011/01/linux-timewhat-do-real-user-and-sys.html
http://yuanfarn.blogspot.tw/2012/08/linux-time.html
