topic Current date & time in posix shell prompt in Operating System - Linux

Current date & time in posix shell prompt

Jaris Detroye — Tue, 10 Oct 2006 16:02:25 GMT

I can not seem to find the right PS1 form to show the current time within the command prompt.

Every time I set it, I get the time in the prompt, but it does not change.
I want the time to be dynamic and reflect the current time when the command prompt is displayed.

Any ideas???

Re: Current date & time in posix shell prompt

Ivan Krastev — Tue, 10 Oct 2006 16:26:26 GMT

Hi Jaris,

you must escape date command in PS1 to be run every time, when PS1 is displayed:

export PS1=`hostname`" ""\$(date )"#

cheers,
ivan

Re: Current date & time in posix shell prompt

Jaris Detroye — Tue, 10 Oct 2006 16:38:58 GMT

I just cut & pasted your PS1 string into my unix shell, and since the $ is escaped it simply prints the string $(date) in the prompt is does not substitute the value.
With the PS1 string:
PS1=`hostname`" ""\$(date)"#

This is what I get:
saturn $(date)#

Re: Current date & time in posix shell prompt

Ivan Krastev — Tue, 10 Oct 2006 17:11:58 GMT

Oops, its my fault - i tested it in ksh.

ivan

Re: Current date & time in posix shell prompt

Peter Godron — Wed, 11 Oct 2006 02:49:45 GMT

Hi Jaris,
modify your ~/.profile to include:
ENV=~/.shrc
export ENV

then edit/create your ~/.shrc to include:
export DATE="$(date '+%d%b')"
export SECONDS="$(date '+3600*%H+60*%M+%S')"
typeset -Z2 _h; typeset -Z2 _m ; typeset -Z2 _s
_hh="(SECONDS/3600)%24"
_mm="(SECONDS/60)%60"
_ss="(SECONDS)%60"
_time='${_x[(_m=_mm)==(_h=_hh)==(_s=_ss)]}$_h:$_m:$_s'
export PS1=$(echo "${DATE}${_time} # ")
set +u

Re: Current date & time in posix shell prompt

Jaris Detroye — Wed, 11 Oct 2006 08:44:04 GMT

Wow. (Pause...)

That's some script.
Work's great!
As I try to dissect it to understand exactly what is going on here, I can't seem to understand why the 'export SECONDS=' line produce a dynamic variable that changes every time you reference it.
I tried the date command with a (less complicated) formatted output string, and it produced a static output not changing until the variable is explicitly set again.

Why is this different?

Re: Current date & time in posix shell prompt

Peter Godron — Wed, 11 Oct 2006 08:50:08 GMT

Jaris,
a quick search of the archive brought the solution:
http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=1017839
Its the re-evaluation of time that makes the difference to just using `date`.

Script just needed a bit of adjusting.

Re: Current date & time in posix shell prompt

James R. Ferguson — Wed, 11 Oct 2006 08:56:10 GMT

Hi Jaris:

David Totsch explained the logic of this solution in this thread:

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=38457&admit=-682735245+1160574500123+28353475

Regards!

...JRF...

Re: Current date & time in posix shell prompt

Jaris Detroye — Wed, 11 Oct 2006 09:10:03 GMT

Thanks for the pointer, I did not come across that thread researching this issue.

I live for these things, my boss thinks it's a waste of time to obsess over these geek things, but this will give me some food for thought to distract me the rest of the day.

Thanks!!!

Re: Current date & time in posix shell prompt

Jaris Detroye — Wed, 11 Oct 2006 11:40:47 GMT

The only modification I made is to include the current path by changing the following line:

export PS1=$(echo "${DATE}${_time}")' @ $PWD #'

Thanks for the lession in obscure shell inner workings.