Seems simple, but couldn't find any answer:
Is it possible to edit a file for the purpose of updating the Linux date instead of using date +%y%m%d -s "DATE" command?
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1Could you give an example of what you are trying to do? Modify a date within a file? Modify the created/accessed time?– bu5hmanCommented Jun 11, 2019 at 15:49
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are you trying to set the system time & date based on the contents of a file?– Jeff Schaller ♦Commented Jun 11, 2019 at 15:50
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@JeffSchaller Actually I want to know which file contains system time and date and whether it is possible to manually edit this file or not by vim editor for example.– A.ACommented Jun 11, 2019 at 15:54
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@bu5hman, I think my comment to Jeff clarifies my purpose– A.ACommented Jun 11, 2019 at 15:56
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1@A.A Clarifications should be made to the question, not left in comments where they may be ignored. Also, what makes you believe that the system time is stored in a file somewhere?– Kusalananda ♦Commented Jun 11, 2019 at 16:15
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1 Answer
There's no file representing the current system time on Linux. Linux gets the current time from the RTCs (real-time clocks) or from external sources like NTP servers, and then keeps track of it internally. The file-like representations of the RTC (/dev/rtc*) are used for configuring and recieving alarms, and can't be used for setting the time. The RTC status file (/proc/driver/rtc) is read-only. See the kernel documentation for details.
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I thought that the command "hwclock --systohc" writes the system clock to RTC, ya?– A.ACommented Jun 11, 2019 at 16:34
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And maybe the "date" command could have a representation file somewhere. Anyway, thank you for your answer. I'm a noob and I must go through the kernel documentation.– A.ACommented Jun 11, 2019 at 16:40
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2Both use system calls.
dateuses theclock_settime(2)function. You can usestraceto examine what the commands actually do.– muruCommented Jun 11, 2019 at 16:43