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在工作中，我曾寫(xiě)過(guò)一個(gè) Shell 腳本，這個(gè)腳本可以從 4 個(gè) NTP 服務(wù)器輪流獲取時(shí)間，然后將最可靠的時(shí)間設(shè)置為系統(tǒng)時(shí)間。因?yàn)槲覀儗?duì)于時(shí)間的要求比較高，需要在短時(shí)間內(nèi)就獲取到正確的時(shí)間。所以我們就需要對(duì)這個(gè)腳本運(yùn)行時(shí)間進(jìn)行測(cè)試，看看從開(kāi)始運(yùn)行到正確設(shè)置時(shí)間需要花費(fèi)多少時(shí)間。
創(chuàng)新互聯(lián)是一家集網(wǎng)站建設(shè),曹縣企業(yè)網(wǎng)站建設(shè),曹縣品牌網(wǎng)站建設(shè),網(wǎng)站定制,曹縣網(wǎng)站建設(shè)報(bào)價(jià),網(wǎng)絡(luò)營(yíng)銷(xiāo),網(wǎng)絡(luò)優(yōu)化,曹縣網(wǎng)站推廣為一體的創(chuàng)新建站企業(yè)，幫助傳統(tǒng)企業(yè)提升企業(yè)形象加強(qiáng)企業(yè)競(jìng)爭(zhēng)力?？沙浞譂M足這一群體相比中小企業(yè)更為豐富、高端、多元的互聯(lián)網(wǎng)需求。同時(shí)我們時(shí)刻保持專(zhuān)業(yè)、時(shí)尚、前沿，時(shí)刻以成就客戶成長(zhǎng)自我，堅(jiān)持不斷學(xué)習(xí)、思考、沉淀、凈化自己，讓我們?yōu)楦嗟钠髽I(yè)打造出實(shí)用型網(wǎng)站。
其實(shí)在工作中，還有很多情況下需要測(cè)試一個(gè)腳本或者程序運(yùn)行多少時(shí)間，特別是對(duì)于時(shí)間性要求比較高的系統(tǒng)更是如此。對(duì)于時(shí)間的測(cè)試，我們可以用到一個(gè)命令：time 。下面我們就詳細(xì)看看如何使用 time 命令來(lái)對(duì)腳本/命令進(jìn)行測(cè)時(shí)。
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
在結(jié)果里，real 表示從我們執(zhí)行 ping 命令到最終按 ctrl+c 終止這段時(shí)間所耗費(fèi)的時(shí)間;user 及 sys 分別表示 ping 命令在用戶空間及內(nèi)核空間所運(yùn)行的時(shí)間。
2. 將時(shí)間信息寫(xiě)入文件
如果我們想把時(shí)間信息直接寫(xiě)入到文件，而不是顯示在屏幕上，那么我們可以使用 -o 選項(xiàng)，并指定寫(xiě)入的文件路徑。
$ /usr/bin/time -o /home/alvin/time-output.txt ping baidu.com
執(zhí)行這個(gè)命令后，ping 命令的輸出結(jié)果依然會(huì)在終端里，而 time 命令的結(jié)果就寫(xiě)入到我們所指定的 time-output.txt 文件里。
-o 選項(xiàng)表示輸出文件不存在就創(chuàng)建，如果存在的話就直接覆蓋重寫(xiě)。如果我們不想覆蓋重寫(xiě)，而是想追加在文件后面，我們可以使用 -a 選項(xiàng)。
$ /usr/bin/time -a /home/smart/time-output.txt ping linoxide.com
3. 顯示更詳細(xì)的時(shí)間信息
time 命令不帶選項(xiàng)的話，顯示的信息量比較少，如果我們想獲得更詳細(xì)的信息，那么我們可以使用 -v 選項(xiàng)。
$ /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
這個(gè)結(jié)果信息就相當(dāng)詳細(xì)了，我們可以獲取到足夠多我們所需要的信息。
4. 自定義輸出格式
默認(rèn)情況下，time 命令只輸出 real，usr，sys 三個(gè)內(nèi)容，如果我們想要個(gè)性化一些，算定義它的輸出格式，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
如果我們想要輸出以下這樣的格式：
Elapsed Time = 0:01:00, Inputs 2, Outputs 1
我們可以這樣自定義：
$ /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
如果你想讓輸出的結(jié)果有換行，可以在對(duì)應(yīng)的地方添加 \n ，比如：
$ /usr/bin/time -f "Elapsed Time = %E \n Inputs %I \n Outputs %O" ping baidu.com
這樣輸出的結(jié)果就類(lèi)似于這樣：
Elapsed Time = 0:03.92
Inputs 0
Outputs 0
分享題目：對(duì)Linux命令運(yùn)行時(shí)間進(jìn)行監(jiān)測(cè)
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