I want to know current system time with microsecond Resolution. date +%s returns Time in seconds since epoch(1-1-1970). How can I get time in microseconds Resolution. How much delay is in querying this value? By delay I mean suppose at time t secs i query and it gives me value t + t' what is t' ?
My Use case: I am recording Videos using multiple Raspberry Pis simulatenously. Now I want to timestamp each frame of videos so that I can align them. Currently for timestamp it's using boot time(time since boot). Boot time is accurate but it's different for each Raspberry Pi. I have configured all Pi's to a NTP Server thus all have same System time. So basically I want the timestamp of System time not Boot Time. How can I do that ?

How do I change the timestamp of a directory and all the sub-folders within that directory to reflect the modification times of the contained files? For example with this directory structure: [Jan 9] root ├── [Jan 3] file1 ├── [Jan 7] file2 ├── [Jan 6] sub1 │   ├── [Jan 2] file3 │   └── [Jan 1] file4 └── [Jan 4] sub2 └── [Jan 8] file5 Here is a one liner to generate that: mkdir -p root/sub1 root/sub2 && touch -d '2018-01-08' root/sub2/file5 && touch -d '2018-01-04' root/sub2/ && touch -d '2018-01-01' root/sub1/file4 && touch -d '2018-01-02' root/sub1/file3 && touch -d '2018-01-06' root/sub1/ && touch -d '2018-01-07' root/file2 && touch -d '2018-01-03' root/file1 && touch -d '2018-01-09' root/ It can be listed with tree -D I'd like to change the timestamps on the three directories to be: [Jan 8] root ├── [Jan 3] file1 ├── [Jan 7] file2 ├── [Jan 2] sub1 │   ├── [Jan 2] file3 │   └── [Jan 1] file4 └── [Jan 8] sub2 └── [Jan 8] file5 Note: - The current timestamps on the directories are completely ignored and the new time stamps are set only based on the contents. - Time stamps bubble up to multiple levels of parent directories. The reason that I'm doing this is for a directory that gets copied with rsync. The directory is checked into git and could get rsynced from any place that has the repository checked out. To ensure that rsync is consistent and idempotent from the various places, I need to ensure that the time stamps and permissions of everything are in a known state. I already have a script that sets the timestamps of files based on when they were committed to git. I also have a script that sets the permissions on all files and directories to a known state. The only portion that I'm struggling with is bubbling time stamps from the files up to parent directories. I would like one line or short script that I can run from the command line to set directory timestamps based on the timestamps of their contents.

I wish to prepend a timestamp to each line of output from a command. For example: foo bar baz would become [2011-12-13 12:20:38] foo [2011-12-13 12:21:32] bar [2011-12-13 12:22:20] baz ...where the time being prefixed is the time at which the line was printed. How can I achieve this?

Now this really is getting me nuts. I installed ptpd on ubuntu 14.04 and it I just can't get this to work to run as a service. In /etc/default/ptpd I have the following entries: START_DAEMON = yes and PTPD_OPTS = "-G -h -b eth0" but that won't work. When I do sudo ptpd -G -h -b eth0 by command line then the program is starting fine. I already tried to put ptpd -G -h -b eth0 into a batch file called usr/local/bin/start.sh and start this file by /etc/rc.local but that won't work too. The program is just not starting automatically. Any kind of help is very appreciated.

I always thought that the timezone is not stored by the filesystem, and that stat would show times formatted with the current timezone of the user, and therefore if I do stat on various files *today* then the timezone should not change. However this answer https://unix.stackexchange.com/questions/119323/stat-command-detail-information suggests the opposite! Different files appear with different timezones! Does anyone know why?

I have a log file with the following structure

1522693524403 entity1,sometext
1522693541466 entity2,sometext
1522693547273 entity1,sometext
...

Now I would like to replace the time from epoch milliseconds to DD.MM.YYYY HH:MM:SS in all of the log files with a bash command on a Debian System. I tried different solutions provided here and on other websites but it did not really work for me.

-32578 **133767.868869**: kfree: call_site=ffffffff810e6f06 ptr=(nil) How to make trace-cmd report time in epoch time? The time by default is I think time since application uptime. This is a requirement to pinpoint exact time of the event. trace-cmd list -O options doesn't help either.

Continuing https://unix.stackexchange.com/a/22822 , how to deduplicate files, given as a list, into hardlinks, while maintaining the timestamps of their directories? Unfortunately, hardlinks changes the time stamps:

$ mkdir d1
$ mkdir d2
$ mkdir d3
$ echo "content" > d1/f1
$ echo "content" > d2/f2
$ echo "content" > d3/f3
$ ls -la --full-time d1 d2 d3
d1:
total 4
drwxr-xr-x  2 username username  60 2025-04-23 17:26:18.624828807 +0200 .
drwxrwxrwt 29 root     root     820 2025-04-23 17:26:07.397001442 +0200 ..
-rw-r--r--  1 username username   8 2025-04-23 17:26:18.624828807 +0200 f1

d2:
total 4
drwxr-xr-x  2 username username  60 2025-04-23 17:26:26.016715230 +0200 .
drwxrwxrwt 29 root     root     820 2025-04-23 17:26:07.397001442 +0200 ..
-rw-r--r--  1 username username   8 2025-04-23 17:26:26.016715230 +0200 f2

d3:
total 4
drwxr-xr-x  2 username username  60 2025-04-23 17:26:29.296664852 +0200 .
drwxrwxrwt 29 root     root     820 2025-04-23 17:26:07.397001442 +0200 ..
-rw-r--r--  1 username username   8 2025-04-23 17:26:29.296664852 +0200 f3
$ hardlink -v -c -M -O -y memcmp d1/f1 d2/f2 d3/f3
Linking /tmp/d1/f1 to /tmp/d2/f2 (-8 B)
Linking /tmp/d1/f1 to /tmp/d3/f3 (-8 B)
Mode:                     real
Method:                   memcmp
Files:                    3
Linked:                   2 files
Compared:                 0 xattrs
Compared:                 2 files
Saved:                    16 B
Duration:                 0.000165 seconds
$ ls -la --full-time d1 d2 d3
d1:
total 4
drwxr-xr-x  2 username username  60 2025-04-23 17:26:18.624828807 +0200 .
drwxrwxrwt 29 root     root     820 2025-04-23 17:27:19.631893228 +0200 ..
-rw-r--r--  3 username username   8 2025-04-23 17:26:18.624828807 +0200 f1

d2:
total 4
drwxr-xr-x  2 username username  60 2025-04-23 17:28:45.922576280 +0200 .
drwxrwxrwt 29 root     root     820 2025-04-23 17:27:19.631893228 +0200 ..
-rw-r--r--  3 username username   8 2025-04-23 17:26:18.624828807 +0200 f2

d3:
total 4
drwxr-xr-x  2 username username  60 2025-04-23 17:28:45.922576280 +0200 .
drwxrwxrwt 29 root     root     820 2025-04-23 17:27:19.631893228 +0200 ..
-rw-r--r--  3 username username   8 2025-04-23 17:26:18.624828807 +0200 f3

As we see, two file have been replaced with hard links, which is good. However, the time stamps of d2 and d3 have been updated. That's NOT what we want. Ideally, we'd like to have a command that gets a list of files from

find /media/my_NTFS_drive -type f -size $(ls -la -- original_file| cut -d' ' -f5)c -exec cmp -s original_file {} \; -exec ls -t {} + 2>/dev/null

and converts them into hard links to original_file. If the time stamps of the hardlinked files are to be the same, change them to the oldest among the time stamps of original_file and its copies. The time stamps of the directories containing original_file and its copies have to be retained. Clearly, all this has to be automated. (No question we can do it with manual inspection and touch. From a user's viewpoint, it could be done with just another switch to hardlinks. As the task seems rather standard, my hope is that in the past decades, someone has already written a standalone program, perhaps even a shell script.)

I am working on an embedded Linux system (kernel-5.10.220). Now I am testing the suspend and resume in this system with a watchdog time as the wakeup source to wake system up from suspend. The watchdog interrupt comes in every 5 seconds, and the script calls sleep 10 to add 10 seconds delay between continous test. And there is NO RTC in system! Here is my testing script.

#!/bin/sh

trap ctrl_c INT

function ctrl_c()
{
    echo "Exiting"
    exit 0
}

count=0
sec=10

while [ true ]
do
    echo ">>>>>>>>>>> Testing suspend $count"
    echo mem > /sys/power/state
    echo ">>>>>>>>>> Testing suspend 0
>>>>>>>>>> Testing suspend 1
>>>>>>>>>> Testing suspend 2
>>>>>>>>>> Testing suspend 3
>>>>>>>>>> Testing suspend 4
>>>>>>>>>> Testing suspend 5
>>>>>>>>>> Testing suspend 6
<<<<<<<<<<< Resumed after suspend

Thu Jan  1 06:33:12 UTC 1970

From the output of date, the script did NOT delay 10 seconds between tests. The real interval of 10 seconds sleeping is about 2 or 3 seconds! So why sleep 10 did NOT sleep for 10 seconds in the suspend and resume testing?

File timestamps precision is limited to one second for EXT3, one microsecond for UFS, and one nanosecond for EXT4 (at least according to experience). Is there any way to determine this based only on filesystem info? The hacky alternatives I can think of are either to limit all my unit tests to seconds (which I do now), or to touch a bunch of files and checking which digits are zero in stat -c %x.

Here is a test file test.applescript:

display dialog "foo" buttons {"OK"} cancel button 1 default button 1

At 4:05 PM I compiled it to test.app:

osacompile -o test.app test.applescript

At 4:07 PM I edited test.applescript by replacing foo with bar, and then compiled it again, overwriting the existing test.app file. (It was overwritten successfully. If I run it, the dialog shows me "bar", not "foo".)

display dialog "bar" buttons {"OK"} cancel button 1 default button 1

osacompile -o test.app test.applescript

But nevertheless the date modified value of test.app is still 4:05 PM. Why is that? How is that possible? Output of stat -x:

File: "test.app"
  Size: 96           FileType: Directory
  Mode: (0755/drwxr-xr-x)         Uid: (  501/    john)  Gid: (   20/   staff)
Device: 1,17   Inode: 79429067    Links: 3
Access: Sun Mar 23 16:05:52 2025
Modify: Sun Mar 23 16:05:52 2025
Change: Sun Mar 23 17:20:48 2025
 Birth: Sun Mar 23 16:05:52 2025

I am trying to obtain the full date (created or modified) of a particular file for passing to another program. I have tried variations of options with the ls command but none provide a full date for files less than 6 months old and I have limit usage of the options. When I try certain options I have seen trying to research this I get the following message: usage: ls [-1ACFHLNRabcdefgilmnopqrstuxEUX] [File...] None of which seems to provide what I needs as far as I can tell so I tried to use the stat command but it is not available to me. I am using the Korn shell on AIX 5.3 which has limited commands available, can anyone suggest another way that I might be able to obtain a file's created or modified date as a full date (either dd/mm/yyyy or yyyy/mm/dd).

Right now I have these commands: my_dir="$HOME/foo/bar"; rm -rf "$my_dir/WebstormProjects/"; rsync -r --exclude=".git" --exclude="node_modules" "$HOME/WebstormProjects/" "$my_dir/WebstormProjects/" instead of removing everything in "$my_dir/WebstormProjects/" and then copying over, I am looking to use rsync such that it will only overwrite files in "$my_dir/WebstormProjects/" if the files in "$HOME/WebstormProjects/" are newer. So something like this: my_dir="$HOME/foo/bar"; rsync -r --newer --exclude=".git" --exclude="node_modules" "$HOME/WebstormProjects/" "$my_dir/WebstormProjects/" **is it possible to copy files only if they are newer than the destination files?** I did some reading: https://www.tecmint.com/sync-new-changed-modified-files-rsync-linux/ it says: > By default, rsync only copies new or changed files from a source to > destination... I assume it does this by comparing relative file paths? Files with the same path/name are considered to be the same?

I'm looking for a command that will read the metadata of a ‘*.mp4’ file and touch the file's timestamp with the creation time of the video. The command should be read-only with respect to the file contents, i.e. hashing the file before and after should yield the same result. Situation: I made the mistake of moving pictures and videos from the internal storage of my phone to an SD card using Android's stock tool to do so (‘Settings’ → ‘Storage’ → ‘Transfer data to SD card’). Unfortunately, this bumped the timestamps of all of the files, and also messed around with directories other than DCIM/ (pictures and videos were also moved from the Download/, image/, Pictures/, and video/ directories). In hindsight it seems silly that I used such a tool (I'd normally use Ghost Commander ), but it appeared as a notification when running low on space and it just looked so easy. I'm now trying to piece back together the timestamps of various pictures and videos. I'm effectively looking for a video equivalent to the following command , which I used to sort out the images in DCIM/100ANDRO/: exiv2 -T mv *.JPG I skimmed through some FFmpeg documentation , but I see no mention of read-only commands or printing timestamps. (Unfortunately for my situation, this approach does not offer a solution for files I didn't create, such as those in Download/, for which I want to appear in the media collection in chronological order of when I obtained them.)

When I use WinSCP to access my SFTP server, it shows me the last modified (changed) date including seconds. If I use sftp on Linux and run ls -l, it only shows the hours and minutes, but no seconds. How can I also show the seconds using sftp, like WinSCP does it? I already checked the sftp man page and the ls options there, but could not find a matching option.

GNU make relies on timestamps to see if a dependency was changed after some file was built. If you make a change during the leap second or an NTP adjustment, is it possible that make will believe the dependency is older than the built file when it really isn't? This would cause the file to never be rebuilt.

I need to scan Linux systems for viruses/malware, on the entire file system. There are few options to consider. - One is normally what users do: Use antivirus to scan system once a day. - The second option is to find files modified in last one day and give that list to antivirus program. I tested following bash command find on directory with 5 million empty files, and it's extremely efficient. date;find /test/ -type f -ctime -1 1>./find_ctime.out 2>./find.errors;date It takes only about 5 seconds. I am using -ctime option just to overcome some program changing modification time using utility such as touch. Most admins when they talk about a system scan, they talk about having antivirus do the complete scan. Is there a reason why find should not be used to get a list of files modified and scan them? EDIT: I have posted following question which _may_ have an answer to why no antivirus seems to use "find" based incremental approach: https://unix.stackexchange.com/questions/787940/is-there-a-way-to-use-linux-find-and-filter-if-specific-process-was-the-only-o

I am trying to find out a way to do incremental antivirus scan. My current approach under evaluation is using "find". You can see relevant question here: https://unix.stackexchange.com/questions/787860/is-there-a-reason-why-i-cant-use-find-to-scan-modified-files-for-viruses-and-ma/ Please note - the question already posted above is using modified time but I found out that clamav scans files even if it is accessed or opened not just modified. The antivirus in question is clamav. Clamav, just like every other AV has option of on access scanning i.e. it would scan a file as soon as it's **acccessed** or **opened**. That means I have to change\use command: find /test/ -type f -atime -1 1>./find_ctime.out 2>./find.errors Unfortunately I cannot use clamav "On Access Scanning" feature - one reason being it's too heavy on system. If I use "find" this is a problem I run into: - I start first scan at 12:00 midnight on 10 files. - When I use "find" next day at 12:00 midnight, I have to give start time at 12:00 midnight previous day. I cannot given start time when scan was finished to find because that would leave system vulnerable. - Problem with this approach is, it would include 10 files clamav (clamscan) accessed yesterday. - I cannot blindly exclude yesterday's list, __even if__ access timestamp was in yesterday's scan window because that will make system vulnerable, even though chances are very small. - and the cycle will repeat next day and so on until it would include ALL files on the system. So I wanted to exclude a file if **only** clamscan\clamdscan has accessed it since last scan. I used stat and do not see any relevant field in output. I also searched in find documentation but I could not find it. Is there a way to use linux "find" and filter if specific process was the only one accessed it? Thanks in advance!

For files within a specific folder, I would like vim to never touch "modified" timestamp at all. The background is that I use Bloxsom for blogging, which uses plain text files in ~/bloxsom as source of all articles. The article date (and therefore order of appearence) is based on modification date of the text file. I don't want article pop up like if it's *new* whenever I just fix a typo. (I do *lots* of them... :D) So far, vim changes timestamp and the original stamp is lost forever. This is OK and I want to keep it that way for most of files on the system. But I don't want that for the blog files - I can always touch the file if I need. Any ideas on how to tweak vim into this behavior?

I can make some date arithmetic with date command like

$ date -u -d '3 days 2024-12-01T00:00:00Z' +%FT%H:%M:%SZ
2024-12-04T00:00:00Z
$

The date command can parse quite a lot of date formats, including ISO-8601 formats. Is there an easy way to make it to interpret also ISO-8601 intervals? Naive approach fails...

$ date -u -d 'PT3D 2024-12-01T00:00:00Z' +%FT%H:%M:%SZ
date: invalid date ‘PT3D 2024-12-01T00:00:00Z’
$