blocks|key|198619|text|理解dmesg时间戳非常简单:它是内核启动以来的时间。因此，有了启动时间(uptime)，您可以将秒数相加，并以您喜欢的任何格式显示它们。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|198620|或者更好的方法是，使用dmesg的-T命令行选项并解析人类可读的格式。|198621|从man+page|198622|-T,+--ctime
++++Print+human+readable+timestamps.+The+timestamp+could+be+inaccurate!

++++The+time+source+used+for+the+logs+is+not+updated+after+system+SUSPEND/RESUME.|code-block|syntax|javascript|198623|entityMap|0|LINK|mutability|MUTABLE|url|http://manpages.ubuntu.com/manpages/raring/en/man1/dmesg.1.html^0|2|5|11|6|0|B|5|H|2|0|1|8|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]|$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|11|8|@$9|12|A|13|B|C]|$9|14|A|15|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|16|8|@]|D|@$9|17|A|18|1|19]]|E|$]]|$1|J|3|K|5|L|7|1A|8|@]|D|@]|E|$M|N]]|$1|O|3|-4|5|6|7|1B|8|@]|D|@]|E|$]]]|P|$Q|$5|R|S|T|E|$U|V]]]]

Understanding <code>dmesg</code> timestamp is pretty simple: it is time in seconds since the kernel started. So, having time of startup (<code>uptime</code>), you can add up the seconds and show them in whatever format you like.

Or better, you could use the <code>-T</code> command line option of <code>dmesg</code> and parse the human readable format.

From the <a href="http://manpages.ubuntu.com/manpages/raring/en/man1/dmesg.1.html" rel="noreferrer">man page</a>:

<pre><code>-T, --ctime
 Print human readable timestamps. The timestamp could be inaccurate!

 The time source used for the logs is not updated after system SUSPEND/RESUME.
</code></pre>

blocks|key|198632|text|您需要在/proc/stat中引用"btime“，这是最近一次引导系统时的Unix纪元时间。然后，您可以基于该系统引导时间，然后加上dmesg中给定的已用秒数来计算每个事件的时间戳。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|198633|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

you will need to reference the "btime" in /proc/stat, which is the Unix epoch time when the system was latest booted. Then you could base on that system boot time and then add on the elapsed seconds given in dmesg to calculate timestamp for each events.

blocks|key|416851|text|对于较老的Linux发行版，另一种选择是使用包装脚本，例如在Perl或Python中。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|416852|请在此处查看解决方案：|416853|http://linuxaria.com/article/how-to-make-dmesg-timestamp-human-readable?lang=en+http://jmorano.moretrix.com/2012/03/dmesg-human-readable-timestamps/|offset|length|416854|entityMap|0|LINK|mutability|MUTABLE|url|http://linuxaria.com/article/how-to-make-dmesg-timestamp-human-readable?lang=en|1|http://jmorano.moretrix.com/2012/03/dmesg-human-readable-timestamps/^0|0|0|0|27|0|28|1W|1|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|S|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|T|8|@]|9|@$F|U|G|V|1|W]|$F|X|G|Y|1|Z]]|A|$]]|$1|H|3|-4|5|6|7|10|8|@]|9|@]|A|$]]]|I|$J|$5|K|L|M|A|$N|O]]|P|$5|K|L|M|A|$N|Q]]]]

With older Linux distros yet another option is to use wrapping script, e.g. in Perl or Python. 

See solutions here:

<a href="http://linuxaria.com/article/how-to-make-dmesg-timestamp-human-readable?lang=en" rel="nofollow">http://linuxaria.com/article/how-to-make-dmesg-timestamp-human-readable?lang=en</a>
<a href="http://jmorano.moretrix.com/2012/03/dmesg-human-readable-timestamps/" rel="nofollow">http://jmorano.moretrix.com/2012/03/dmesg-human-readable-timestamps/</a>

blocks|key|198698|text|在dr+answer的帮助下，我写了一个变通方法，可以将put转换为put。如果你没有任何时间戳或者已经正确的时间戳，它不会破坏任何东西。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|198699|dmesg_with_human_timestamps+()+{
++++$(type+-P+dmesg)+"$@"+%7C+perl+-w+-e+'use+strict;
++++++++my+($uptime)+=+do+{+local+@ARGV="/proc/uptime";<>};+($uptime)+=+($uptime+=~+/%5E(\d%2B)\./);
++++++++foreach+my+$line+(<>)+{
++++++++++++printf(+($line=~/%5E\[\s*(\d%2B)\.\d%2B\](.%2B)/)+?+(+"[%25s]%25s\n",+scalar+localtime(time+-+$uptime+%2B+$1),+$2+)+:+$line+)
++++++++}'
}
alias+dmesg=dmesg_with_human_timestamps|code-block|syntax|javascript|198700|此外，还可以很好地了解dmesg时间戳转换逻辑以及如何在没有时间戳时启用时间戳：https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solutionid=sk92677|198701|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/users/115655/dr|1|https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solutionid=sk92677^0|1|2|0|0|0|14|35|1|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]]|C|$]]|$1|D|3|E|5|F|7|Y|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|Z|8|@]|9|@$A|10|B|11|1|12]]|C|$]]|$1|K|3|-4|5|6|7|13|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]|S|$5|N|O|P|C|$Q|T]]]]

With the help of <a href="https://stackoverflow.com/users/115655/dr">dr</a> answer, I wrote a workaround that makes the conversion to put in your .bashrc. It won't break anything if you don't have any timestamp or already correct timestamps.

<pre><code>dmesg_with_human_timestamps () {
 $(type -P dmesg) "$@" | perl -w -e 'use strict;
 my ($uptime) = do { local @ARGV="/proc/uptime";&lt;&gt;}; ($uptime) = ($uptime =~ /^(\d+)\./);
 foreach my $line (&lt;&gt;) {
 printf( ($line=~/^\[\s*(\d+)\.\d+\](.+)/) ? ( "[%s]%s\n", scalar localtime(time - $uptime + $1), $2 ) : $line )
 }'
}
alias dmesg=dmesg_with_human_timestamps
</code></pre>

Also, a good reading on the dmesg timestamp conversion logic &amp; how to enable timestamps when there are none:
<a href="https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&amp;solutionid=sk92677" rel="noreferrer">https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&amp;solutionid=sk92677</a>

blocks|key|416923|text|在dmesg的最新版本中，您可以直接调用dmesg+-T。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|416924|entityMap^0|K|8|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

In recent versions of dmesg, you can just call <code>dmesg -T</code>.

blocks|key|416968|text|所以KevZero要求一个不那么笨拙的解决方案，所以我想出了以下几点：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|416969|sed+-r+'s#%5E\[([0-9]%2B\.[0-9]%2B)\](.*)#echo+-n+"[";echo+-n+$(date+--date="@$(echo+"$(grep+btime+/proc/stat%7Ccut+-d+"+"+-f+2)%2B\1"+%7C+bc)"+%2B"%25c");echo+-n+"]";echo+-n+"\2"#e'|code-block|syntax|javascript|416970|下面是一个例子：|416971|$+dmesg%7Ctail+%7C+sed+-r+'s#%5E\[([0-9]%2B\.[0-9]%2B)\](.*)#echo+-n+"[";echo+-n+$(date+--date="@$(echo+"$(grep+btime+/proc/stat%7Ccut+-d+"+"+-f+2)%2B\1"+%7C+bc)"+%2B"%25c");echo+-n+"]";echo+-n+"\2"#e'
[2015-12-09T04:29:20+COT]+cfg80211:+++(57240000+KHz+-+63720000+KHz+@+2160000+KHz),+(N/A,+0+mBm),+(N/A)
[2015-12-09T04:29:23+COT]+wlp3s0:+authenticate+with+dc:9f:db:92:d3:07
[2015-12-09T04:29:23+COT]+wlp3s0:+send+auth+to+dc:9f:db:92:d3:07+(try+1/3)
[2015-12-09T04:29:23+COT]+wlp3s0:+authenticated
[2015-12-09T04:29:23+COT]+wlp3s0:+associate+with+dc:9f:db:92:d3:07+(try+1/3)
[2015-12-09T04:29:23+COT]+wlp3s0:+RX+AssocResp+from+dc:9f:db:92:d3:07+(capab=0x431+status=0+aid=6)
[2015-12-09T04:29:23+COT]+wlp3s0:+associated
[2015-12-09T04:29:56+COT]+thinkpad_acpi:+EC+reports+that+Thermal+Table+has+changed
[2015-12-09T04:29:59+COT]+i915+0000:00:02.0:+BAR+6:+[???+0x00000000+flags+0x2]+has+bogus+alignment
[2015-12-09T05:00:52+COT]+thinkpad_acpi:+EC+reports+that+Thermal+Table+has+changed|416972|如果您希望它的性能更好一些，请将proc中的时间戳放入一个变量中:)|416973|entityMap|0|LINK|mutability|MUTABLE|url|https://reddit.com/u/KevZero^0|2|7|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@$A|X|B|Y|1|Z]]|C|$]]|$1|D|3|E|5|F|7|10|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|11|8|@]|9|@]|C|$]]|$1|K|3|L|5|F|7|12|8|@]|9|@]|C|$G|H]]|$1|M|3|N|5|6|7|13|8|@]|9|@]|C|$]]|$1|O|3|-4|5|6|7|14|8|@]|9|@]|C|$]]]|P|$Q|$5|R|S|T|C|$U|V]]]]

So <a href="https://reddit.com/u/KevZero" rel="noreferrer">KevZero</a> requested a less kludgy solution, so I came up with the following:

<pre><code>sed -r 's#^\[([0-9]+\.[0-9]+)\](.*)#echo -n "[";echo -n $(date --date="@$(echo "$(grep btime /proc/stat|cut -d " " -f 2)+\1" | bc)" +"%c");echo -n "]";echo -n "\2"#e'
</code></pre>

Here's an example:

<pre><code>$ dmesg|tail | sed -r 's#^\[([0-9]+\.[0-9]+)\](.*)#echo -n "[";echo -n $(date --date="@$(echo "$(grep btime /proc/stat|cut -d " " -f 2)+\1" | bc)" +"%c");echo -n "]";echo -n "\2"#e'
[2015-12-09T04:29:20 COT] cfg80211: (57240000 KHz - 63720000 KHz @ 2160000 KHz), (N/A, 0 mBm), (N/A)
[2015-12-09T04:29:23 COT] wlp3s0: authenticate with dc:9f:db:92:d3:07
[2015-12-09T04:29:23 COT] wlp3s0: send auth to dc:9f:db:92:d3:07 (try 1/3)
[2015-12-09T04:29:23 COT] wlp3s0: authenticated
[2015-12-09T04:29:23 COT] wlp3s0: associate with dc:9f:db:92:d3:07 (try 1/3)
[2015-12-09T04:29:23 COT] wlp3s0: RX AssocResp from dc:9f:db:92:d3:07 (capab=0x431 status=0 aid=6)
[2015-12-09T04:29:23 COT] wlp3s0: associated
[2015-12-09T04:29:56 COT] thinkpad_acpi: EC reports that Thermal Table has changed
[2015-12-09T04:29:59 COT] i915 0000:00:02.0: BAR 6: [??? 0x00000000 flags 0x2] has bogus alignment
[2015-12-09T05:00:52 COT] thinkpad_acpi: EC reports that Thermal Table has changed
</code></pre>

If you want it to perform a bit better, put the timestamp from proc into a variable instead :)

blocks|key|198850|text|对于没有"dmesg+-T“的系统，比如RHEL/CentOS6，我喜欢lucas-cimon之前提供的"dmesg_with_human_timestamps”函数。不过，它在一些运行时间较长的机器上遇到了一些问题。事实证明，dmesg中的内核时间戳是从单个CPU保存的正常运行时间值派生而来的。随着时间的推移，这会与实时时钟不同步。因此，最新dmesg条目的最准确转换将基于CPU时钟，而不是/proc/uptime。例如，在特定的CentOS+6.6机器上：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|198851|#+grep+"\.clock"+/proc/sched_debug++%7C+head+-1
++.clock+++++++++++++++++++++++++:+32103895072.444568
#+uptime
+15:54:05+up+371+days,+19:09,++4+users,++load+average:+3.41,+3.62,+3.57
#+cat+/proc/uptime
32123362.57+638648955.00|code-block|syntax|javascript|198852|考虑到以毫秒为单位的CPU正常运行时间，这里有将近5个半小时的偏移量。因此，我修改了脚本并在此过程中将其转换为本机bash：|198853|dmesg_with_human_timestamps+()+{
++++FORMAT="%25a+%25b+%25d+%25H:%25M:%25S+%25Y"

++++now=$(date+%2B%25s)
++++cputime_line=$(grep+-m1+"\.clock"+/proc/sched_debug)

++++if+[[+$cputime_line+=~+[%5E0-9]*([0-9]*).*+]];+then
++++++++cputime=$((BASH_REMATCH[1]+/+1000))
++++fi

++++dmesg+%7C+while+IFS=+read+-r+line;+do
++++++++if+[[+$line+=~+%5E\[\+*([0-9]%2B)\.[0-9]%2B\]\+(.*)+]];+then
++++++++++++stamp=$((now-cputime%2BBASH_REMATCH[1]))
++++++++++++echo+"[$(date+%2B"${FORMAT}"+--date=@${stamp})]+${BASH_REMATCH[2]}"
++++++++else
++++++++++++echo+"$line"
++++++++fi
++++done
}

alias+dmesgt=dmesg_with_human_timestamps|198854|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/users/636849/lucas-cimon^0|10|B|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]]|C|$]]|$1|D|3|E|5|F|7|Y|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|Z|8|@]|9|@]|C|$]]|$1|K|3|L|5|F|7|10|8|@]|9|@]|C|$G|H]]|$1|M|3|-4|5|6|7|11|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]]]

For systems without "dmesg -T" such as RHEL/CentOS 6, I liked the "dmesg_with_human_timestamps" function provided by <a href="https://stackoverflow.com/users/636849/lucas-cimon">lucas-cimon</a> earlier. It has a bit of trouble with some of our boxes with large uptime though. Turns out that kernel timestamps in dmesg are derived from an uptime value kept by individual CPUs. Over time this gets out of sync with the real time clock. As a result, the most accurate conversion for recent dmesg entries will be based on the CPU clock rather than /proc/uptime. For example, on a particular CentOS 6.6 box here:

<pre><code># grep "\.clock" /proc/sched_debug | head -1
 .clock : 32103895072.444568
# uptime
 15:54:05 up 371 days, 19:09, 4 users, load average: 3.41, 3.62, 3.57
# cat /proc/uptime
32123362.57 638648955.00
</code></pre>

Accounting for the CPU uptime being in milliseconds, there's an offset of nearly 5 1/2 hours here. So I revised the script and converted it to native bash in the process:

<pre><code>dmesg_with_human_timestamps () {
 FORMAT="%a %b %d %H:%M:%S %Y"

 now=$(date +%s)
 cputime_line=$(grep -m1 "\.clock" /proc/sched_debug)

 if [[ $cputime_line =~ [^0-9]*([0-9]*).* ]]; then
 cputime=$((BASH_REMATCH[1] / 1000))
 fi

 dmesg | while IFS= read -r line; do
 if [[ $line =~ ^\[\ *([0-9]+)\.[0-9]+\]\ (.*) ]]; then
 stamp=$((now-cputime+BASH_REMATCH[1]))
 echo "[$(date +"${FORMAT}" --date=@${stamp})] ${BASH_REMATCH[2]}"
 else
 echo "$line"
 fi
 done
}

alias dmesgt=dmesg_with_human_timestamps
</code></pre>

blocks|key|198892|text|与date命令输出不同，dmesg+-T可能显示错误的时间。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|198893|解决方法是使用-k日志with+-dmesg。我使用的是-k，因为它更短：|198894|journalctl+-k|code-block|syntax|javascript|198895|它将只显示内核消息和正确的时间。|198896|要仅显示匹配短语的内核行，请执行以下操作：|198897|journalctl+-kg+phrase|198898|entityMap^0|1|4|C|8|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Z|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|10|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|11|8|@]|D|@]|E|$]]|$1|O|3|P|5|6|7|12|8|@]|D|@]|E|$]]|$1|Q|3|R|5|J|7|13|8|@]|D|@]|E|$K|L]]|$1|S|3|-4|5|6|7|14|8|@]|D|@]|E|$]]]|T|$]]

<code>dmesg -T</code> may show wrong time, different from <code>date</code> command output.
Workaround is journalctl with -k, --dmesg. I am using -k as it is shorter:
<pre><code>journalctl -k
</code></pre>
It will show only kernel messages and correct time.
To show only kernel lines matching phrase:
<pre><code>journalctl -kg phrase
</code></pre>

I am trying to understand the <code>dmesg</code> timestamp and find it hard to convert that to change it to java date/custom date format.
Sample dmesg log:
<pre><code>[14614.647880] airo(eth1): link lost (missed beacons)
</code></pre>
So how do I convert <code>14614.647880</code> to a standard date?

How do I convert dmesg timestamp to custom date format?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我正在尝试理解dmesg时间戳，并发现很难将其转换为java日期/自定义日期格式。dmesg日志示例：[14614.647880] airo(eth1): link lost (missed beacons)那么如何将14614.647880转换为标准日期呢？

问如何将dmesg时间戳转换为自定义日期格式？
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问如何将dmesg时间戳转换为自定义日期格式？EN