内置printf可以打印当前时间(以毫秒或纳秒为单位) [英] Printing current time in milliseconds or nanoseconds with printf builtin

问题描述

我们可以使用内置的printf函数打印当前时间，而无需调用像date这样的外部命令，

We can print the current time with the builtin printf function, without needing to invoke an external command like date, like this:

printf '%(%Y-%m-%d:%H:%M:%S)T %s\n' -1
# sample output: 2019-03-30:17:39:36,846

我们如何使printf也可以打印毫秒或纳秒?在格式字符串中使用%3N或%N无效:

How can we make printf to print milliseconds or nanoseconds as well? Using %3N or %N in the format string doesn't work:

printf '%(%Y-%m-%d:%H:%M:%S,%3N)T %s\n' -1 # outputs 2019-03-30:17:38:16,%3N
printf '%(%Y-%m-%d:%H:%M:%S,%N)T %s\n' -1  # outputs 2019-03-30:17:38:16,%N

但是，date命令可以正常工作:

However, the date command works fine:

date +%Y-%m-%d:%H:%M:%S,%3N # gives 2019-03-30:17:39:36,846
date +%Y-%m-%d:%H:%M:%S,%N  # gives 2019-03-30:17:39:36,160643077

这是在Red Hat Linux 7.3版上.

This is on a Red Hat Linux version 7.3.

推荐答案

在bash 5中，您可以从EPOCHREALTIME获得微秒精度.但是，printf本身无法直接访问它，因此您需要自己提取微秒.

In bash 5, you can get microsecond precision from EPOCHREALTIME. However, printf itself has no way to access that directly, so you need to extract the microseconds yourself.

$ echo $EPOCHREALTIME; printf '%(%F:%T)T.%d\n' "$EPOCHSECONDS" "${EPOCHREALTIME#*.}"; echo $EPOCHREALTIME
1554006709.936990
2019-03-31:00:31:49.937048
1554006709.937083

这需要一些时间，但结果似乎准确到大约0.05毫秒.

This takes a little time, but the result appears to be accurate to about 0.05 milliseconds.

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