Linux中的两个time

Linux中有两个time命令，一个bash的内置time，一个GNU time。

[root@wingwu ~]# type -a time
time is a shell keyword
time is /usr/bin/time


bash time 很简单，它只是显示程序的执行时间，没什么可用的参数。

[root@wingwu ~]# time date
2010年 04月 26日 星期一 20:49:05 CST

real 0m0.009s
user 0m0.001s
sys 0m0.003s


GNU time 除了显示程序的执行时间，同时也会显示很多其它信息：内存、I/O和IPC Call等信息。

[root@wingwu ~]# /usr/bin/time -v date
2010年 04月 26日 星期一 20:50:29 CST
        Command being timed: "date"
        User time (seconds): 0.00
        System time (seconds): 0.00
        Percent of CPU this job got: 0%
        Elapsed (wall clock) time (h:mm:ss or m:ss): 0:00.00
        Average shared text size (kbytes): 0
        Average unshared data size (kbytes): 0
        Average stack size (kbytes): 0
        Average total size (kbytes): 0
        Maximum resident set size (kbytes): 0
        Average resident set size (kbytes): 0
        Major (requiring I/O) page faults: 0
        Minor (reclaiming a frame) page faults: 202
        Voluntary context switches: 1
        Involuntary context switches: 2
        Swaps: 0
        File system inputs: 0
        File system outputs: 0
        Socket messages sent: 0
        Socket messages received: 0
        Signals delivered: 0
        Page size (bytes): 4096
        Exit status: 0


通过man time可用查看到这两个命令的相关信息。