Hi,

I have some important text info going to standard output.
I want to try my best to have the user see it.

Here is my problem.
If I know the user is using the program (let's say a shell program) in an X11 environment, I could make sure the text is out by using xterm -e <exe name>.
The problem is how do I know xterm is runnable - it needs an X or similar GUI environent.

Thanks.

oldbee

An idea is to try first to run xterm and to check the exit value of the program. If it returns 0 then everything was fine and the results were printed using xterm. If not the try using just a shell in the console. If you specify language I can help you find the appropriate functions to use.

Good idea!

One question thou...
If xterm -e <cmd> fails, how do I know it is because of xterm failed (in this case I just run cmd without xterm) or cmd failed (I should not retry cmd anymore)

I am using bash.

Thanks.

oldbee

Well... the return value to the script that runs xterm would be the return value of xterm. That means that if $? is not equal to zero, then xterm did not execute correctly. One thing should be aware of is that if the cmd of 'xterm -e cmd' fails to execute, the error will be printed in the xterm that has opened... An idea of making error checking to that file is to not execute the command directly. Execute a script that will execute cmd and will check if it exited without problems. e.g.

#!/bin/bash
#matrying script
cmd
if [ $? != 0 ]; then touch cmd.error;fi

Then you can check from the first script if cmd.error exists by an 'if [ -e cmd.error ]; then...'. You can even logout from the xterm that the cmd is executed if you add an exit command at the end of matrying script and you can execute it with 'xterm -hold -e matrying'. Don't forget to give permission to execute matrying. Hope that helps!
Whoa! You keep making me think! This is tiring you know ;-P

Thanks Parapente. It helps!

An easier way would be to check to see if the $DISPLAY variable is set. If it is then you probably have an X server available, otherwise you don't.

The thing is dorward that you never know when there will be a strange program to use the display environment variable. It is indeed clever to use the DISPLAY, but the above mentioned way would not fail even in extreme situations that DISPLAY is set though you have no X server up. The choice is on oldbee. Another variable he can use is that of TERM. When in X-windows it gets the value xterm usually. But that is usually and not always...

I agree with parapente. I thought about DISPLAY, but noticed it is just not "enough".
Thank you all.

well yeah, having an X server running does not mean you are actually using it at that time...

dorward's suggestion to use the DISPLAY is probably best I think. That's how this test is most often done.

Using xterm to test, assumes that the user has a working xterm installed, and xterm is in their path, and that they have permission to run it. It also has the overhead of starting an xterm session.

just my $0.02