How to check the number of terminals open from inside a shell script

[sumatheja]

Hi All,
        I'm can anyone let me know if there's some variable holding
the value of the total number of terminals open. I have a requirement
where i need to execute some script only first time a terminal is
opened. I feel this is not the right place to post this but will be
glad if someone can help me out.

--
cheers
Sumatheja Dasararaju

[JB]

sumatheja <sumatheja <at> gmail.com> writes:
> ...

$ w
$ who

JB

[JB]

JB <jb.1234abcd <at> gmail.com> writes:
> ...

$ who am i

[Mark Liggett]

Hi Sumatheja,

I'm guessing you want a script to run only once (did say whether it was per user).  You could add your script to the .bashrc file - this way the script would run once when the user logs on.  Alternatively run the script and export an environment variable - then check it using an if statement before you run the script again, eg;

if [ -n "$script-has-run-envar" ]; then
    <source_script>
    script-has-run-envar="Yes"
    export $script-has-run-envar
fi

Check the lifecycle of the environment variable is what you need though.

Mark

On 29/10/2010 12:26, "sumatheja"  wrote:

Hi All,
        I'm can anyone let me know if there's some variable holding
the value of the total number of terminals open. I have a requirement
where i need to execute some script only first time a terminal is
opened. I feel this is not the right place to post this but will be
glad if someone can help me out.

--
cheers
Sumatheja Dasararaju
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[Joachim Backes]

On 10/29/2010 03:39 PM, Mark Liggett wrote:
> Hi Sumatheja,
>
> I’m guessing you want a script to run only once (did say whether it was
> per user).  You could add your script to the .bashrc file – this way the
> script would run once when the user logs on.  Alternatively run the
> script and export an environment variable – then check it using an if
> statement before you run the script again, eg;
>
> if [ -n “$script-has-run-envar” ]; then
>     <source_script>
>     script-has-run-envar=”Yes”
>     export $script-has-run-envar

I think you mean -without the $ char-  ;-)

export script-has-run-envar

Regards

[Mark Liggett]

Whoops - apologies.  Friday afternoon :-)

On 29/10/2010 16:26, "Joachim Backess" 
wrote:
> On 10/29/2010 03:39 PM, Mark Liggett wrote:
> > Hi Sumatheja,
> >
> > I¹m guessing you want a script to run only once (did say whether it was
> > per user).  You could add your script to the .bashrc file ­ this way the
> > script would run once when the user logs on.  Alternatively run the
> > script and export an environment variable ­ then check it using an if
> > statement before you run the script again, eg;
> >
> > if [ -n ³$script-has-run-envar² ]; then
> >     <source_script>
> >     script-has-run-envar=²Yes²
> >     export $script-has-run-envar
>
> I think you mean -without the $ char-  ;-)
>   export script-has-run-envar
>
> Regards

[Suvayu Ali]

On 29 October 2010 06:39, Mark Liggett  wrote:
> You could add your script to the .bashrc file – this way the script would
> run once when the user logs on.

I presume you meant ~/.bash_profile ? ~/.bashrc is sourced every time
a user opens a terminal, whereas ~/.bash_profile is sourced every time
a user logs in. This distinction however becomes redundant when the
user always uses a text terminal to login. (as in no gui)

[Cameron Simpson]

On 29Oct2010 09:52, suvayu ali  wrote:
| On 29 October 2010 06:39, Mark Liggett  wrote:
| > You could add your script to the .bashrc file – this way the script would
| > run once when the user logs on.
| 
| I presume you meant ~/.bash_profile ? ~/.bashrc is sourced every time
| a user opens a terminal, whereas ~/.bash_profile is sourced every time
| a user logs in. This distinction however becomes redundant when the
| user always uses a text terminal to login. (as in no gui)

Not if they run a subshell. For example, a shell escape from an editor,
or a screen session, or ...

The number of bugs in the .bashrc suggestion is high. $ signs, dahses
instead of underscores, .bashrc instead of .bash_profile, presuming the
user users bash at all (I don't if I can help it, myself - zsh has
better facilities), not working at all anyway, since another login
wouldn't see the exported variable anyway, not actually looking at
terminals at all...

But the OP needs to clarify what he/she means by "number of open
terminals" (for this user? only showing in "who"? or other terminals?
etc) and whether that is actaully what they need or just what they
think _indicates_ what they actually need.

What he/she actually asks for is difficult to do properly. Hopefully it isn't
what they need.

Cheers,