Script shell echo result of command has unknown values

Question

I try to echo the result of a command. But my problem is that the result has strange values at the end and I can not delete them.

My result after the command is for example:

fnRead 

results to 12. Juni 13:32:18 2028 þ§

But I only need 12. Juni 13:32:18 2028 because I want to check the equivalence of two strings

My code that generates this output is a function:

fnRead() {
    echo $(cat /dev/rtc)
}

I tried to cut off the last strings but it will only remove numbers from the year.

Im working with shell scripts by the way.

Note that simply cat /dev/rtc would do the job; there's no need for the command substitution and echo. — Jonathan Leffler
– Jonathan Leffler, Commented Jul 21, 2015 at 14:14
sry forgot to mention that the cat /dev/rtc is inside a function. I use $(cat /dev/rtc) to execute the command and getting the result als an echo — JPM
– JPM, Commented Jul 21, 2015 at 14:19
OK; working out context can be tricky. It's not unreasonable to need var=$(cat /dev/rtc) — or, in Bash, var=$(</dev/rtc) — to assign to a variable for later use and then echo for debugging/checking purposes. Separately, haven't they fixed things like this by the year 2028? I was hoping things would have improved by then. And thank you for dropping back to chat with us. Does this mean that SO doesn't exist still in 2028? — Jonathan Leffler
– Jonathan Leffler, Commented Jul 21, 2015 at 14:21
Very funny ;) I can rewrite this date. This was only an example for my format of date. I am writing tests in shell script. Therefore it is important to know which date was written into the chip — JPM
– JPM, Commented Jul 21, 2015 at 14:28

user2591612 · Accepted Answer · 2015-07-21 14:11:44Z

2

According to documentation, you need to use hwclock to read/write from /dev/rtc. You are seeing a raw output of this interface.

See also: http://linux.die.net/man/4/rtc

answered Jul 21, 2015 at 14:11

user2591612

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3 Comments

JPM Over a year ago

there are several ways to get the time. I need to use both commands. hwclock which uses ioctl and cat /dev/rtc which uses rtc_read function. This is because I wrote my own rtc driver.

Jonathan Leffler Over a year ago

Are you sure your RTC driver is doing what it is supposed to do?

JPM Over a year ago

Yes ;) Its for educational purpose only. I have to set a range of years which the chip can handle. So its possible for me to write time in the future

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