我想在一些不同的条件下在linux shell中执行一些东西，并且能够输出每次执行的执行时间。
我知道我可以写一个perl或python脚本，可以做到这一点，但有一种方法我可以在shell中做到这一点吗?(恰好是bash)
当前回答
使用内置的time关键字:
$ help time
time: time [-p] PIPELINE
Execute PIPELINE and print a summary of the real time, user CPU time,
and system CPU time spent executing PIPELINE when it terminates.
The return status is the return status of PIPELINE. The `-p' option
prints the timing summary in a slightly different format. This uses
the value of the TIMEFORMAT variable as the output format.
例子:
$ time sleep 2
real 0m2.009s user 0m0.000s sys 0m0.004s
其他回答
要逐行测量delta，请尝试用指针测量。
$ npm install -g gnomon
$ <your command> | gnomon --medium=1.0 --high=4.0 --ignore-blank --real-time=100
一个命令行实用程序，有点像moreutils的ts，用于将时间戳信息预先添加到另一个命令的标准输出中。对于长时间运行的流程非常有用，因为您需要记录花费如此长时间的事情。
还可以使用——high和/或——medium选项指定以秒为单位的长度阈值，超过该阈值，gnomon将以红色或黄色突出显示时间戳。你还可以做一些其他的事情。
如果您只需要精确到秒，您可以使用内置的$SECONDS变量，该变量计算shell已经运行的秒数。
while true; do
start=$SECONDS
some_long_running_command
duration=$(( SECONDS - start ))
echo "This run took $duration seconds"
if some_condition; then break; fi
done
方法是
$ > g++ -lpthread perform.c -o per
$ > time ./per
输出为>>
real 0m0.014s
user 0m0.010s
sys 0m0.002s
一个可能简单的方法(可能不能满足不同用户的需求)是使用shell PROMPT。这是一个简单的解决方案，在某些情况下可能有用。你可以使用bash提示功能，如下例所示:
export PS1='[\t \u@\h]\$'
上面的命令将导致shell提示符更改为:
[HH:MM:SS username@hostname]$
每次运行命令(或按回车键)返回到shell提示符时，提示符将显示当前时间。
notes: 1) beware that if you waited for sometime before you type your next command, then this time need to be considered, i.e the time displayed in the shell prompt is the timestamp when the shell prompt was displayed, not when you enter command. some users choose to hit Enter key to get a new prompt with a new timestamp before they are ready for the next command. 2) There are other available options and modifiers that can be used to change the bash prompt, refer to ( man bash ) for more details.
使用内置的time关键字:
$ help time
time: time [-p] PIPELINE
Execute PIPELINE and print a summary of the real time, user CPU time,
and system CPU time spent executing PIPELINE when it terminates.
The return status is the return status of PIPELINE. The `-p' option
prints the timing summary in a slightly different format. This uses
the value of the TIMEFORMAT variable as the output format.
例子:
$ time sleep 2
real 0m2.009s user 0m0.000s sys 0m0.004s
