Linux file date and time

File Timestamps — mtime, ctime and atime in Linux

When you are working with directory and files, you may need to know about Linux file timestamps such as change time (ctime), access time (atime), and modification time (mtime). Linux files, directories, sockets have three different timestamps – mtime, ctime and atime.

Probably when working in Linux you have get answers to following questions:

When was the last date of file content modified? When was the file last opened/accessed ? When the properties of the file such as ownership, permissions last changed?

Here, we are going to explain each file timestamps in Linux in detail.

mtime – Last modification time

Mtime or modification time is the time of the last change to the file contents. ‘Modification’ means something inside the file was amended or deleted, or new data was added.

Use the -l (long listing) option with ls, you can see the modified timestamp.

ctime – last change time

Ctime is the changed timestamp referring to changes made to attribute of a file such as ownership, access permission. It’s the time at which the metadata related to the file changed.

To see the change timestamp, use the -lc option:-

atime – last access time

Atime or access timestamp is the last time a file was read, read by one of the processes directly or through commands and scripts.

Use the -lu (access time) option with command ls to see access time. You can see the modification time and access time for the same file are different.

Show mtime, atime and ctime with stat command

Most of the linux distribution come with stat command which can be used to show all of the time stamp in a more convenient way.

To see modification time, access time and change time of a particular file use as follow:-

The timestamp are first generated in number of seconds since the Unix epoch, it translates the number of seconds into a date and time from the system time zone.

Conclusion

Unfortunately, we won’t be able to find file creation time using ctime, atime or mtime orelse we have to use debugfs command.

In this article, we learned about Linux file timestamps and about access time, modification time, and change time. Your feedback is much welcome.

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Display Date And Time In Linux

H ow do I display date and time in Linux using the command line and GUI options?

To display date and time under Linux operating system using command prompt use the date command. It can also display the current time / date in the given FORMAT. We can set the system date and time as root user too.

Tutorial details
Difficulty level	Easy
Root privileges	No
Requirements	Linux with the terminal application
Est. reading time	3 minutes

Syntax

Open a terminal and type the following command:
date

You can format the date as follows in dd-mm-yy format:
date +»%d-%m-%y»

Simply display the current time:
date «+%T»

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To print the date of the day before yesterday, run:
date —date=’2 days ago’
Want to see the day of year of Christmas in the current year? Try:
date —date=’25 Dec’ +%j
Display the current full month name and the day of the month:
date ‘+%B %d’

Display date and time in Linux using the timedatectl

Most modern Linux distro with systemd use the timedatectl command. It is used to query and change the system clock and its settings, and enable or disable time synchronization services. All you have to do is type the following command:
$ timedatectl

TZ environment variable

The TZ environment tells Linux what time zone you are in. Many times when you want to change your time zone temporarily. For example, you might want to print the current date and time in “America/Los_Angeles” timezone even though you are in “Europe/London”. So we can set TZ, give a command like as follows when using TCSH/CSH:
setenv TZ timezone
For BASH/KSH/SH (see export command:
TZ=timezone; export TZ
Another option:
TZ=»America/Los_Angeles» date
TZ=»Asia/Tokyo» date
Use the following command to print a list of all timezones:
timedatectl list-timezones
timedatectl list-timezones | more
## filter out data using the grep command/egrep command ##
timedatectl list-timezones | grep -i Hong_kong
timedatectl list-timezones | grep -i paris
timedatectl list-timezones | grep -E -i ‘paris|london|kolkata’

The TZ Environment Variable on Linux

GUI Tool: Time Administration

The Time Administration Tool allows you to set the time, date and timezone of your system, as well as setting any time server to synchronize your local time server. Type the following command to start time admin tool:
sudo time-admin
## OR ##
time-admin

Fig.01: Linux Date and Time Administration Tool

How to change date and time settings with Gnome based Linux desktop

First, you need to Settings in Activities and then click Details in the sidebar. Make sure you click Date & Time in the sidebar to open the panel:

Conclusion

In this quick tutorial, you learned about the date command that you can use to see or change the date/time under Linux operating systems. We further explained how to use the GUI tools too. The date command has many more options. See man page by typing the following man command:
$ man date

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How to Find and Sort Files Based on Modification Date and Time in Linux

Usually, we are in habit of saving a lot of information in form of files on our system. Some, hidden files, some kept in a separate folder created for our ease of understanding, while some as it is. But, this whole stuff fills our directories; usually desktop, making it look like a mess. But, the problem arises when we need to search for a particular file modified on particular date and time in this huge collection.

Find and Sort Files by Date and Time in Linux

People comfortable with GUI’s can find it using File Manager, which lists files in long listing format, making it easy to figure out what we wanted, but those users having habit of black screens, or even anyone working on servers which are devoid of GUI’s would want a simple command or set of commands that could ease out their search.

Real beauty of Linux shows here, as Linux has a collection of commands which if used separately or together can help to search for a file, or sort a collection of files according to their name, date of modification, time of creation, or even any filter you could think of applying to get your result.

Here, we will unveil the real strength of Linux by examining a set of commands which can help sorting a file or even a list of files by Date and Time.

Linux Utilities to Sort Files in Linux

Some basic Linux command line utilities that are just sufficient for sorting a directory based on Date and Time are:

ls command

ls – Listing contents of directory, this utility can list the files and directories and can even list all the status information about them including: date and time of modification or access, permissions, size, owner, group etc.

We’ve already covered many articles on Linux ls command and sort command, you can find them below:

sort command

sort – This command can be used to sort the output of any search just by any field or any particular column of the field.

We’ve already covered two articles on Linux sort command, you can find them below:

These commands are in themselves very powerful commands to master if you work on black screens and have to deal with lots of files, just to get the one you want.

Some Ways to Sort Files using Date and Time

Below are the list of commands to sort based on Date and Time.

1. List Files Based on Modification Time

The below command lists files in long listing format, and sorts files based on modification time, newest first. To sort in reverse order, use ‘-r’ switch with this command.

2. List Files Based on Last Access Time

Listing of files in directory based on last access time, i.e. based on time the file was last accessed, not modified.

3. List Files Based on Last Modification Time

Listing of files in directory based on last modification time of file’s status information, or the ‘ctime’ . This command would list that file first whose any status information like: owner, group, permissions, size etc has been recently changed.

If ‘-a’ switch is used with above commands, they can list and sort even the hidden files in current directory, and ‘-r’ switch lists the output in reverse order.

For more in-depth sorting, like sorting on Output of find command, however ls can also be used, but there ‘sort’ proves more helpful as the output may not have only file name but any fields desired by user.

Below commands show usage of sort with find command to sort the list of files based on Date and Time.

To learn more about find command, follow this link: 35 Practical Examples of ‘find’ Command in Linux

4. Sorting Files based on Month

Here, we use find command to find all files in root (‘/’) directory and then print the result as: Month in which file was accessed and then filename. Of that complete result, here we list out top 11 entries.

The below command sorts the output using key as first field, specified by ‘-k1’ and then it sorts on Month as specified by ‘M’ ahead of it.

5. Sort Files Based on Date

Here, again we use find command to find all the files in root directory, but now we will print the result as: last date the file was accessed, last time the file was accessed and then filename. Of that we take out top 11 entries.

The below sort command first sorts on basis of last digit of the year, then sorts on basis of last digit of month in reverse order and finally sorts on basis of first field. Here, ‘1.8‘ means 8th column of first field and ‘n’ ahead of it means numerical sort, while ‘r’ indicates reverse order sorting.

6. Sorting Files Based on Time

Here, again we use find command to list out top 11 files in root directory and print the result in format: last time file was accessed and then filename.

The below command sorts the output based on first column of the first field of the output which is first digit of hour.

7. Sorting Ouptut of ls -l based on Date

This command sorts the output of ‘ls -l’ command based on 6th field month wise, then based on 7th field which is date, numerically.

Conclusion

Likewise, by having some knowledge of sort command, you can sort almost any listing based on any field and even its any column you desire. These were some of tricks to help you sort files based on Date or Time. You can have your own tricks build based on these. However, if you have any other interesting trick, you can always mention that in your comments.

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Find Files By Access, Modification Date / Time Under Linux or UNIX

I do not remember where I saved pdf and text files under Linux. I have downloaded files from the Internet a few months ago. How do I find my pdf or text files?

You need to use the find command. Each file has three time stamps, which record the last time that certain operations were performed on the file:

You can search for files whose time stamps are within a certain age range, or compare them to other time stamps.

You can use -mtime option. It returns list of file if the file was last accessed N*24 hours ago. For example to find file in last 2 months (60 days) you need to use -mtime +60 option.

• -mtime +60 means you are looking for a file modified 60 days ago.
• -mtime -60 means less than 60 days.
• -mtime 60 If you skip + or – it means exactly 60 days.

So to find text files that were last modified 60 days ago, use
$ find /home/you -iname «*.txt» -mtime -60 -print

Display content of file on screen that were last modified 60 days ago, use
$ find /home/you -iname «*.txt» -mtime -60 -exec cat <> \;

Count total number of files using wc command
$ find /home/you -iname «*.txt» -mtime -60 | wc -l

You can also use access time to find out pdf files. Following command will print the list of all pdf file that were accessed in last 60 days:
$ find /home/you -iname «*.pdf» -atime -60 -type -f

List all mp3s that were accessed exactly 10 days ago:
$ find /home/you -iname «*.mp3» -atime 10 -type -f

There is also an option called -daystart. It measure times from the beginning of today rather than from 24 hours ago. So, to list the all mp3s in your home directory that were accessed yesterday, type the command
$ find /home/you -iname «*.mp3» -daystart -type f -mtime 1

• -type f – Only search for files and not directories

-daystart option

The -daystart option is used to measure time from the beginning of the current day instead of 24 hours ago. Find out all perl (*.pl) file modified yesterday, enter:

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