UNIX for Dummies Questions & Answers

Hello,

I'm trying to write a bash script that will query the current system time (OS X 10.6.6) and then convert the output from HH:MM:SS into time in seconds. The output of the system time command (systemsetup -gettime) is returned as:

Time: HH:MM:SS

so I wanted to use awk -F: to grab HH:MM:SS

From the command line I can:

Code:

prompt: systemsetup -gettime ; a=$(systemsetup -gettime) ; echo $a | awk -F: '{print $2":"$3":"$4}'
  Time: 22:32:59 <-- output of systemsetup -gettime
   22:32:59 <-- tells me that I want to capture $2, $3, and $4

How do I assign $2, $3, and $4 from awk to the variables hr, min, and sec?

Thank you all in advance!

---------- Post updated at 06:21 PM ---------- Previous update was at 10:26 AM ----------

Sorry, I didn't know how to use the code tags.

I found a different method to capture the hours, minutes, and seconds, so in the above example I now have:

Code:

d=$ref_time
IFS=":"
set -- $d
hr=$2
min=$3
sec=$4

# strip leading white space from hr
hr=$(echo $hr | tr -d " ")

so if ref_time was set to "Time: 22:32:59" then

Code:

prompt: echo $ref_time
Time: 22:32:59
prompt: echo $hr $min $sec
22 32 59

I would now like to re-assemble hr, min, and sec into a single variable. I tried variations of:

Code:

set_time=$hr":"$min":"$sec

but with everything I've tried echo $set_time still returns 22 32 59 and I need it to return 22:32:59 with the :'s.

Any advice?

this | that | other | awk is overkill for this. And you don't need the systemsetup command either.

Code:

read HH MM SS <<< $(date '+%H %M %S')

and ding, they're in shell variables.
Then you strip off the leading zeroes

Code:

HH=${HH#0}
MM=${MM#0}
SS=${SS#0}

...and add the whole mess together:

Code:

S=$((SS + (MM*60) + (HH*60*60) ))
echo $S

Or, if you want epoch seconds, you can do it all in one with

Code:

date +%s

Thanks for the tips!

Using epoch time is very intriguing because it avoids a lot of the pain of converting back and forth between HH:MM:SS and seconds, but I'm having trouble setting the system time with date and using epoch time. Any reason to use date over systemsetup?

I was able to solve my problem with using a colon as a separator. Earlier in the script I used IFS=":" to parse HH MM SS from systemsetup -gettime. I unset IFS after grabing my init values and everything seems to be working just fine.

Thanks to all for your help and insights!

For one thing, you'll find GNU date in Linux as well as OSX. For another thing, I'm guessing that date is a less heavyweight utility than systemsetup.

To get epoch seconds from GNU date, you just do date +%s

To set the date with epoch seconds, I think you do date -s @192342... where 192342... is your epoch seconds of course and @ tells date that it's epoch seconds. Just one of the little things you have to dig real deep into date's info files to find.

---------- Post updated at 01:08 PM ---------- Previous update was at 01:05 PM ----------

You can set IFS for individual lines and nothing else by prefixing the line. Like: IFS=":" read HH MM SS < datafile Though IFS of course can have side-effects on how parameters expand so be careful what you put on the right-hand side.

You can also use IFS to seperate things into arrays for you.

Code:

OLDIFS="${IFS}"
IFS=":"
ARRAY=( ${SOMETHING_WITH_COLONS_IN_IT} )
IFS="${OLDIFS}"

Again, much thanks!

I am going to try incorporating several of the suggestions you made. I have noticed when running the version of the script that I came up with I get an occasional system message that appears to be the result of a pre-dated timestamp somewhere, but otherwise is doing the job for which it was intended. My thinking was that systemsetup would work better with regards to any daemons running int he background, but perhaps date is the right tool for the job? I did have trouble getting the clock to set using date when you originally suggested it, but had not come across the -s @epoch_seconds syntax.

All the best!

The man page for GNU date is almost blank, nearly all the useful information's in the info file. Which is a real pain since info is.