time命令
time是 BASH shell 中内建的关键字
[root@server ~]# which time
/usr/bin/which: no time in (/usr/local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin)
[root@server ~]# type -a time
time is a shell keyword
[root@server ~]# help time
time: time [-p] pipeline
Report time consumed by pipeline's execution.
Execute PIPELINE and print a summary of the real time, user CPU time,
and system CPU time spent executing PIPELINE when it terminates.
Options:
-p print the timing summary in the portable Posix format
The value of the TIMEFORMAT variable is used as the output format.
Exit Status:
The return status is the return status of PIPELINE.
times: times
Display process times.
Prints the accumulated user and system times for the shell and all of its
child processes.
Exit Status:
Always succeeds.
[root@server ~]# time cd
real 0m0.000s
user 0m0.000s
sys 0m0.000s
real —— 指的是命令或程序所花费的总时间
user —— 指的是在用户模式下程序所花费的时间
sys —— 指的是在内核模式下程序所花费的时间