In particular, you can simply write that: The solution above is highly portable - even beyond the limits of shell programming.īut when using GNU date as we do on Linux for example, we have access to a whole world of subtleties to express the date. Using the mighty powers of GNU date utils Display the result using the required format Remove two hours (expressed as a number of seconds) Convert to nbr of seconds since Unix Epoch So here is a possible solution to my issue:
and the symbol to specify an input date is expressed as a number of seconds since the Epoch (BSD will use the -r option for that purpose). the %s specifier to convert a date to the number of seconds since the Epoch]. In practice, in Unix-like systems, the reference date is usually 00:00:00 UTC on 1 January 1970 - sometimes known as Unix Epoch (hence the name of the traitor in Matrix - you remember him?). Finally, using the same facilities as in the initial step, we can convert back the result to a date time format. Having that numeric quantity, we can now use classic arithmetics to add or remove homogeneous quantities (say remove 7200s - that is 2×60×60s - to obtain the date it was two hours ago). Usually, we convert dates to a number of seconds (or milliseconds) since some reference time. When faced with similar problems, the typical solution will be to convert the (human readable) date and time to some numeric quantity. Here we are using the Bash, and we have to rely on the date tool for our purpose. That being said, which options do we still have? Any decent programming language should have some facilities to deal with time specific issues. If you really need an argument to convince you, think for example about issues with daylight saving time. I strongly discourage you from taking the path I used in my initial attempt: never do date and time calculations by yourself. Minus-two-hours "1 01:10:42" What was the problem?ĭate arithmetic is much more complicated that one might expect. I came to a solution using simple shell arithmetics:Įcho "$" The function output must follow the YYYY-MM-DD hh:mm format. How to install the NVIDIA drivers on Ubuntu 18.This week, I want a shell function to display the date & time it was two hours ago. How to Install Adobe Acrobat Reader on Ubuntu 20.04 Focal Fossa Linux. 
Set Kali root password and enable root login.
How to change from default to alternative Python version on Debian Linux.Netplan static IP on Ubuntu configuration.How to enable/disable firewall on Ubuntu 18.04 Bionic Beaver Linux.How to install Tweak Tool on Ubuntu 20.04 LTS Focal Fossa Linux.Linux IP forwarding – How to Disable/Enable.How to use bash array in a shell script.AMD Radeon Ubuntu 20.04 Driver Installation.How to install missing ifconfig command on Debian Linux.Ubuntu 20.04 Remote Desktop Access from Windows 10.How to find my IP address on Ubuntu 20.04 Focal Fossa Linux.How to install the NVIDIA drivers on Ubuntu 20.04 Focal Fossa Linux.$ date echo `date -universal +%s` + 1468823 | bc To add 2 weeks, 3 days, and 23 seconds, use the same process but use addition instead of subtraction:.Echo time to universal human readable date format: The only thing left to do is convert output.$ date echo `date -universal +%s` - 1468823 | bc Since this would be 1,468,823 seconds ago, the calculation would look like this:
Lets see how we can subtract 2 weeks, 3 days, and 23 seconds from a current date using epoch time. 
Therefore, epoch time “1” using universal time is: epoch time is simply a number of seconds since “00:00:00”. In this case here as a simple example on how to the do all above using epoch time. On some Unix systems the date syntax described above may not be available.
0 kommentar(er)
