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linux 时间命令

在工作中,我曾写过一个 Shell 脚本,这个脚本可以从 4 个 NTP 服务器轮流获取时间,然后将最可靠的时间设置为系统时间。因为我们对于时间的要求比较高,需要在短时间内就获取到正确的时间。所以我们就需要对这个脚本运行时间进行测试,看看从开始运行到正确设置时间需要花费多少时间。

linux 时间命令

其实在工作中,还有很多情况下需要测试一个脚本或者程序运行多少时间,特别是对于时间性要求比较高的系统更是如此。对于时间的测试,我们可以用到一个命令:time 。下面我们就详细看看如何使用 time 命令来对脚本/命令进行测时。

1. time 命令基本用法

time 命令最基本的用法,就是 time + 命令 ,比如:

$ time ping baidu.com  PING baidu.com (123.125.114.144) 56(84) bytes of data.  64 bytes from 123.125.114.144 (123.125.114.144): icmp_seq=1 ttl=56 time=2.83 ms  64 bytes from 123.125.114.144 (123.125.114.144): icmp_seq=2 ttl=56 time=2.77 ms  …………  ^C  --- baidu.com ping statistics ---  8 packets transmitted, 8 received, 0% packet loss, time 10818ms  rtt min/avg/max/mdev = 2.765/2.808/2.862/0.039 ms    real    0m11.173s  user    0m0.004s  sys     0m0.002s  

在结果里,real 表示从我们执行 ping 命令到最终按 ctrl+c 终止这段时间所耗费的时间;user 及 sys 分别表示 ping 命令在用户空间及内核空间所运行的时间。

2. 将时间信息写入文件

如果我们想把时间信息直接写入到文件,而不是显示在屏幕上,那么我们可以使用 -o 选项,并指定写入的文件路径。

$ /usr/bin/time -o /home/alvin/time-output.txt ping baidu.com 

执行这个命令后,ping 命令的输出结果依然会在终端里,而 time 命令的结果就写入到我们所指定的 time-output.txt 文件里。

-o 选项表示输出文件不存在就创建,如果存在的话就直接覆盖重写。如果我们不想覆盖重写,而是想追加在文件后面,我们可以使用 -a 选项。

$ /usr/bin/time -a /home/smart/time-output.txt ping linoxide.com 

3. 显示更详细的时间信息

time 命令不带选项的话,显示的信息量比较少,如果我们想获得更详细的信息,那么我们可以使用 -v 选项。

$ /usr/bin/time -v ping baidu.com  PING baidu.com (123.125.114.144) 56(84) bytes of data.  64 bytes from 123.125.114.144 (123.125.114.144): icmp_seq=1 ttl=56 time=2.75 ms  64 bytes from 123.125.114.144 (123.125.114.144): icmp_seq=2 ttl=56 time=2.76 ms  64 bytes from 123.125.114.144 (123.125.114.144): icmp_seq=3 ttl=56 time=2.85 ms  64 bytes from 123.125.114.144 (123.125.114.144): icmp_seq=4 ttl=56 time=2.77 ms  ^C  --- baidu.com ping statistics ---  4 packets transmitted, 4 received, 0% packet loss, time 3300ms  rtt min/avg/max/mdev = 2.751/2.785/2.851/0.075 ms          Command being timed: "ping baidu.com"          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): 0:03.64          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): 2140          Average resident set size (kbytes): 0          Major (requiring I/O) page faults: 0          Minor (reclaiming a frame) page faults: 626          Voluntary context switches: 10          Involuntary context switches: 0          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  

这个结果信息就相当详细了,我们可以获取到足够多我们所需要的信息。

4. 自定义输出格式

默认情况下,time 命令只输出 real,usr,sys 三个内容,如果我们想要个性化一些,算定义它的输出格式,time 命令也是支持的。time 命令支持的格式有很多,如下所示:

C - Name and command line arguments used  D - Average size of the process's unshared data area in kilobytes  E - Elapsed time in a clock format  F - Number of page faults  I - Number of file system inputs by the process  K - Average total memory use of the process in kilobytes  M - Maximum resident set the size of the process during the lifetime in Kilobytes  O - Number of file system outputs by the process  P - Percentage of CPU that the job received  R - Number of minor or recoverable page faults  S - Total number of CPU seconds used by the system in kernel mode  U - Total number of CPU seconds used by user mode  W - Number of times the process was swapped out of main memory  X - Average amount of shared text in the process  Z - System's page size in kilobytes  c - Number of times the process was context-switched  e - Elapsed real time used by the process in seconds  k - Number of signals delivered to the process  p - Average unshared stack size of the process in kilobytes  r - Number of socket messages received by the process  s - Number of socket messages sent by the process  t - Average resident set size of the process in kilobytes  w - Number of time the process was context-switched voluntarily  x - Exit status of the command  

如果我们想要输出以下这样的格式:

Elapsed Time = 0:01:00, Inputs 2, Outputs 1 

我们可以这样自定义:

$ /usr/bin/time -f "Elapsed Time = %E, Inputs %I, Outputs %O" ping baidu.com  PING baidu.com (220.181.38.148) 56(84) bytes of data.  64 bytes from 220.181.38.148 (220.181.38.148): icmp_seq=1 ttl=54 time=1.82 ms  64 bytes from 220.181.38.148 (220.181.38.148): icmp_seq=2 ttl=54 time=1.86 ms  ^C  --- baidu.com ping statistics ---  4 packets transmitted, 4 received, 0% packet loss, time 3003ms  rtt min/avg/max/mdev = 1.825/1.859/1.879/0.056 ms  Elapsed Time = 0:03.92, Inputs 0, Outputs 0 

如果你想让输出的结果有换行,可以在对应的地方添加 n ,比如:

$ /usr/bin/time -f "Elapsed Time = %E n Inputs %I n Outputs %O" ping baidu.com 

这样输出的结果就类似于这样:

Elapsed Time = 0:03.92  Inputs 0  Outputs 0  

原文来自:https://os.51cto.com/art/202004/613848.htm

本文地址:https://www.linuxprobe.com/linux-command-runtime-test.html编辑:冯瑞涛,审核员:逄增宝

Linux命令大全:https://www.linuxcool.com/

linux 时间命令

本文由博客一文多发平台 OpenWrite 发布!

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