Linux clock command

Linux Command Manual

The Linux clock command is used to adjust the RTC time.

RTC is the built-in hardware time of the computer. Executing this command can display the current time, adjust the hardware clock time, set the system time to be consistent with the hardware clock time, or save the system time back to the hardware clock.

Syntax

clock [--adjust][--debug][--directisa][--getepoch][--hctosys][--set --date="<date and time>"][--setepoch --epoch=< >][--show][--systohc][--test][--utc][--version]

Parameter Description:

• --adjust for the first time--set parameter or--systohc parameter sets the hardware clock, and will/A file named adjtime is generated under the etc directory. When these two parameters are used to adjust the hardware clock again, this file will record the difference between the two adjustments, and later execute the clock command with the following--adjust"parameter, the program will automatically calculate the average value according to the recorded file value difference, and automatically adjust the time of the hardware clock.
• --debug 　Display detailed command execution process, convenient for troubleshooting or understanding the execution of the program.
• --directisa 　Tell the clock command not to go through/dev/rtc device file, directly access the hardware clock. This parameter is applicable to old computers with only ISA bus structure.
• --getepoch 　Present the new era value of the hardware clock in the system core to the standard output device.
• --hctosys 　Hardware Clock to System Time，set the system time to be consistent with the hardware clock. Since this action will cause the system to update the access time of files in full, it is best to execute it when the system starts.
• --set--date 　Set the date and time of the hardware clock.
• --setepoch--epoch=<year> 　Set the new era value of the hardware clock of the system core, represented by four-digit numbers.
• --show 　Read the time of the hardware clock and present it to the standard output device.
• --systohc 　System Time to Hardware Clock，save the system time back to the hardware clock.
• --test 　Only for testing, does not really write the time to the hardware clock or system time.
• --utc 　Set the hardware clock time to CUT, sometimes also called UTC or UCT.
• --version 　Display version information.

Online Examples

Get the Current Time

# clock //Get the Current Time

Display UTC Time

# clock -utc //Display UTC Time

Linux Command Manual