lak wrote:
> I want to change PS1 prompt to my system time.
> For that I wrote PS1='\T'. But This will get effect only when i press
> enter.
> I want to update PS1 to current time without pressing enter?
> How can i do this?
>
You need to change its definition in your shell startup file which is in
your home directory, probably called .bashrc or .login

Robert

On Oct 31, 11:04 am, lak wrote:
> I want to change PS1 prompt to my system time.
> For that I wrote PS1='\T'. But This will get effect only when i press
> enter.
> I want to update PS1 to current time without pressing enter?
> How can i do this?

You can not do that. Not any shell that I know of will make a separate
thread and use control characters just to do something totally
inappropriate and inpractical.

Cheers,
Darko

On Oct 31, 3:04 pm, lak wrote:
> I want to change PS1 prompt to my system time.
> For that I wrote PS1='\T'. But This will get effect only when i press
> enter.
> I want to update PS1 to current time without pressing enter?
> How can i do this?

Give the following entry in $HOME/.bash_profile of the user for which
you want to change the prompt

export PS1='[\T]$ '

or if you want to set it for all the users , give the same entry in /
etc/profile

Logout and relogin, you'll get the new prompt. To revert to the
original prompt, remove the entry 4m the file and relogin.

Meenakshi.

meenakshi wrote:
> On Oct 31, 3:04 pm, lak wrote:
>> I want to change PS1 prompt to my system time.
>> For that I wrote PS1='\T'. But This will get effect only when i press
>> enter.
>> I want to update PS1 to current time without pressing enter?
>> How can i do this?
>
> Give the following entry in $HOME/.bash_profile of the user for which
> you want to change the prompt
>
> export PS1='[\T]$ '

Hmm, I tried that, and as I expected, it didn't somehow make the
time update "without pressing enter".

- Logan

Logan Shaw writes:
>meenakshi wrote:
>> On Oct 31, 3:04 pm, lak wrote:
>>> I want to change PS1 prompt to my system time.
>>> For that I wrote PS1='\T'. But This will get effect only when i press
>>> enter.
>>> I want to update PS1 to current time without pressing enter?
>>> How can i do this?
>>
>> Give the following entry in $HOME/.bash_profile of the user for which
>> you want to change the prompt
>>
>> export PS1='[\T]$ '

>Hmm, I tried that, and as I expected, it didn't somehow make the
>time update "without pressing enter".


None of the respondants get what you are asking. What you are asking
for can't be done.

You have to think of the Unix CLI in terms of that it was designed for TTY's.
Print a line on the paper, read a line the user types in.

It doesn't have provisions for updating the data display continously.

Not that some new program couldn't be written to do that, but in general,
the shells are still stuck in the day and age of TTYs. Hard copy print.

On Oct 31, 3:04 am, lak wrote:
> I want to change PS1 prompt to my system time.
> For that I wrote PS1='\T'. But This will get effect only when i press
> enter.
> I want to update PS1 to current time without pressing enter?
> How can i do this?

I guess you can get the source code of any shell and modify the code
to do what you want. You can add a timeout while the shell is waiting
for input. After time out, you print \r with new system time. If the
shell input is in line mode, then this will affect your input if you
are typing something . If the shell input is in character mode, then
you can stop the timeout when the first character is received, and
just wait for more input with \n at the end. But, that will not tell
you when the command line was completed and you will handle the input
characters (left arrow, right arrow, del, backspace, etc.)

I use tcsh, and the command history will show the time for each
command. But, it does not show date (maybe it is configurable). Is
that what you want?

Hsing

2007-10-31, 03:04(-07), lak:
> I want to change PS1 prompt to my system time.
> For that I wrote PS1='\T'. But This will get effect only when i press
> enter.
> I want to update PS1 to current time without pressing enter?
> How can i do this?

You may be able to get something close enough in zsh with:

RPS1=%D{%H:%M:%S}'
trap 'zle -I; echoti cuu1' ALRM
TMOUT=1

Personnaly, I use GNU screen, with which I can have the time in
a status bar or in the window title. You can also tell your
shell to update part of screen's status bar.

--
Stéphane

Doug McIntyre wrote:
> Logan Shaw writes:
>> meenakshi wrote:
>>> On Oct 31, 3:04 pm, lak wrote:
>>>> I want to change PS1 prompt to my system time.
>>>> For that I wrote PS1='\T'. But This will get effect only when i press
>>>> enter.
>>>> I want to update PS1 to current time without pressing enter?
>>>> How can i do this?
>>> Give the following entry in $HOME/.bash_profile of the user for which
>>> you want to change the prompt
>>>
>>> export PS1='[\T]$ '
>
>> Hmm, I tried that, and as I expected, it didn't somehow make the
>> time update "without pressing enter".

> None of the respondants get what you are asking. What you are asking
> for can't be done.

I think you mean none of the respondents get what meenakshi was asking,
not what I was asking. I wasn't the person asking the question; I just
was pointing out that the person answering it didn't give an answer
that works.

- Logan

2007-11-01, 20:36(+00), Stephane CHAZELAS:
> 2007-10-31, 03:04(-07), lak:
>> I want to change PS1 prompt to my system time.
>> For that I wrote PS1='\T'. But This will get effect only when i press
>> enter.
>> I want to update PS1 to current time without pressing enter?
>> How can i do this?
>
> You may be able to get something close enough in zsh with:
>
> RPS1=%D{%H:%M:%S}'
> trap 'zle -I; echoti cuu1' ALRM
> TMOUT=1

Better:

PS1="%{$terminfo[sc]%}$PS1"
PS2="%{$terminfo[sc]%}$PS2"
PS3="%{$terminfo[sc]%}$PS3"
RPS1='%D{%H:%M:%S}'
trap 'zle -I; echoti rc' ALRM
TMOUT=1

>
> Personnaly, I use GNU screen, with which I can have the time in
> a status bar or in the window title. You can also tell your
> shell to update part of screen's status bar.

--
Stéphane

2007-11-01, 16:03(+00), Doug McIntyre:
[...]
> None of the respondants get what you are asking. What you are asking
> for can't be done.
>
> You have to think of the Unix CLI in terms of that it was designed for TTY's.
> Print a line on the paper, read a line the user types in.
>
> It doesn't have provisions for updating the data display continously.
>
> Not that some new program couldn't be written to do that, but in general,
> the shells are still stuck in the day and age of TTYs. Hard copy print.

I can't see why not. Fish does syntax higlighting on the fly,
zsh provides with a completion system where completions are
being displayed in colors (à la GNU ls) and selectable with the
cursor keys. A curses module for zsh is currently being
developped which promisses some nice future zsh features.

Most modern terminal emulators have enhanced capabilities
including a wide range of colors (most support 256 now), mouse
support, font switching... A shell (when interactive) being a
terminal application like any other, I can't see why it couldn't
use those capabilities.

--
Stéphane

On Fri, 02 Nov 2007 09:13:28 GMT, Stephane CHAZELAS
wrote:

>2007-11-01, 16:03(+00), Doug McIntyre:
>[...]
>> None of the respondants get what you are asking. What you are asking
>> for can't be done.
>>
>> You have to think of the Unix CLI in terms of that it was designed for TTY's.
>> Print a line on the paper, read a line the user types in.
>>
>> It doesn't have provisions for updating the data display continously.
>>
>> Not that some new program couldn't be written to do that, but in general,
>> the shells are still stuck in the day and age of TTYs. Hard copy print.
>
>I can't see why not. Fish does syntax higlighting on the fly,
>zsh provides with a completion system where completions are
>being displayed in colors (à la GNU ls) and selectable with the
>cursor keys. A curses module for zsh is currently being
>developped which promisses some nice future zsh features.
>
>Most modern terminal emulators have enhanced capabilities
>including a wide range of colors (most support 256 now), mouse
>support, font switching... A shell (when interactive) being a
>terminal application like any other, I can't see why it couldn't
>use those capabilities.

The fact that the shell is capable of displaying colours and so on is
irrelevant. The point Doug was making was that when the shell is
waiting for input, it is just _waiting_. There is no 'background'
thread running which can update the display while the main thread is
waiting.
--
PGP key ID 0xEB7180EC

2007-11-02, 09:31(+00), Keith Willis:
[...]
> The fact that the shell is capable of displaying colours and so on is
> irrelevant. The point Doug was making was that when the shell is
> waiting for input, it is just _waiting_. There is no 'background'
> thread running which can update the display while the main thread is
> waiting.

There's nothing preventing the shell to have a background thread,
or an alarm(2) ready to kick in. At least zsh has support for
scheduled jobs.

bash, ksh and zsh are able to arm alarms (via $TMOUT), but only
zsh apparently is able to make use of them as I demonstrated in
another post.

zsh also has the ability to watch additional file descriptors
and to act when there's input comming in. So, it can react on
external input while it's sitting waiting for use input. See zle
-F. That's how I implemented mouse support for zsh with gpm on
the Linux console for instance
(http://stchaz.free.fr/mouse.zsh).

You can do things like

exec 6< <(cmd that generates events)
zle -F 6 zsh-function-that-handles-those-events

For instance.

--
Stéphane

On Nov 1, 5:03 pm, Doug McIntyre wrote:
> Logan Shaw writes:
> >meenakshi wrote:
> >> On Oct 31, 3:04 pm, lak wrote:
> >>> I want to change PS1 prompt to my system time.
> >>> For that I wrote PS1='\T'. But This will get effect only when i press
> >>> enter.
> >>> I want to update PS1 to current time without pressing enter?
> >>> How can i do this?
>
> >> Give the following entry in $HOME/.bash_profile of the user for which
> >> you want to change the prompt
>
> >> export PS1='[\T]$ '
> >Hmm, I tried that, and as I expected, it didn't somehow make the
> >time update "without pressing enter".
>
> None of the respondants get what you are asking. What you are asking
> for can't be done.
>
> You have to think of the Unix CLI in terms of that it was designed for TTY's.
> Print a line on the paper, read a line the user types in.
>
> It doesn't have provisions for updating the data display continously.
>
> Not that some new program couldn't be written to do that, but in general,
> the shells are still stuck in the day and age of TTYs. Hard copy print.

Maybe if you read carefully, you would have seen that I've already
pointed to the same fact (above).

As for reprogramming the shell, why not, yes, you can even program it
yourself and make it your shell, but it won't be bash nor any of the
currently available shells. But in bash, no, you can't do that.

Stephane CHAZELAS wrote:
> There's nothing preventing the shell to have a background thread,
> or an alarm(2) ready to kick in. At least zsh has support for
> scheduled jobs.
>
> bash, ksh and zsh are able to arm alarms (via $TMOUT), but only
> zsh apparently is able to make use of them as I demonstrated in
> another post.

bash (and ksh, I think) can also respond asynchronously to other types
of events. For instance, witness the effects of "set -o notify".

Also, I've never tried using select() (or equivalents like poll()) on
a terminal, but it seems like a shell might be able to use select()
with a timeout if it wanted to display a clock.

Having said all that, the historical context of Unix is that there
are actually 3 environments in which the shell might execute:
(1) non-interactive
(2) teletype (cursor cannot move around screen randomly)
(3) interactive terminal

There's no reason a shell couldn't theoretically update the time
every second on a teletype, but it would probably be a waste of paper
and ink if it did. :-)

- Logan

On Nov 3, 9:18 am, Logan Shaw wrote:
> Stephane CHAZELAS wrote:
> > There's nothing preventing the shell to have a background thread,
> > or an alarm(2) ready to kick in. At least zsh has support for
> > scheduled jobs.
>
> > bash, ksh and zsh are able to arm alarms (via $TMOUT), but only
> > zsh apparently is able to make use of them as I demonstrated in
> > another post.
>
> bash (and ksh, I think) can also respond asynchronously to other types
> of events. For instance, witness the effects of "set -o notify".
>
> Also, I've never tried using select() (or equivalents like poll()) on
> a terminal, but it seems like a shell might be able to use select()
> with a timeout if it wanted to display a clock.
>
> Having said all that, the historical context of Unix is that there
> are actually 3 environments in which the shell might execute:
> (1) non-interactive
> (2) teletype (cursor cannot move around screen randomly)
> (3) interactive terminal
>
> There's no reason a shell couldn't theoreticallyupdatethe time
> every second on a teletype, but it would probably be a waste of paper
> and ink if it did. :-)
>
> - Logan

OK thank you friends for replying to me.

2007-11-02, 23:18(-05), Logan Shaw:
> Stephane CHAZELAS wrote:
>> There's nothing preventing the shell to have a background thread,
>> or an alarm(2) ready to kick in. At least zsh has support for
>> scheduled jobs.
>>
>> bash, ksh and zsh are able to arm alarms (via $TMOUT), but only
>> zsh apparently is able to make use of them as I demonstrated in
>> another post.
>
> bash (and ksh, I think) can also respond asynchronously to other types
> of events. For instance, witness the effects of "set -o notify".

ITYM "synchronously" above. Every POSIX shell supports that.

Here, they respond to the SIGCHLD signal.

You could do things like:
trap '((sleep 1; kill -s USR1 "$$") &)' USR1
kill -s USR1 "$$"

to have something done about every second. However, with those
shells, I don't think there's a command to redisplay the prompt.

> Also, I've never tried using select() (or equivalents like poll()) on
> a terminal, but it seems like a shell might be able to use select()
> with a timeout if it wanted to display a clock.

That's what zsh does when you install a handler for a specific
fd with zsh -F.

> Having said all that, the historical context of Unix is that there
> are actually 3 environments in which the shell might execute:
> (1) non-interactive
> (2) teletype (cursor cannot move around screen randomly)
> (3) interactive terminal
>
> There's no reason a shell couldn't theoretically update the time
> every second on a teletype, but it would probably be a waste of paper
> and ink if it did. :-)
[...]

But $TERM will tell the shell what type of terminal it is
dealing with and it is already adapting its behavior to it.

--
Stéphane