Re: Viewing multiple .png files simultaneously

On 2007-09-19, philbo30 wrote:
On Sep 19, 10:19 am, "Chris F.A. Johnson" <cfajohn...@xxxxxxxxx>
wrote:
On 2007-09-19, Josef Moellers wrote:
Chris F.A. Johnson wrote:
On 2007-09-19, philbo30 wrote:
...

ImageMagick is just the tool I was looking for; it works great. The
only additional thing I would like to do is specify the amount of time
that the image displays. As an example, I want it to display for 60
seconds. I didn't see that capability associated with the "display"
application, but then again I didn't look that much either. Ideas?

display ... &
sleep 5
kill "$!"

<pedantic>
make that
display ... &
sleep 60
kill $!
</pedantic>

What if IFS is not the default? E.g.:

$ (> IFS=1234567890
sleep 20 &
sleep 2
kill $!
)

bash: kill: `': not a pid or valid job spec
bash: kill: `': not a pid or valid job spec
bash: kill: `': not a pid or valid job spec
bash: kill: `': not a pid or valid job spec
$

But:

$ (> IFS=1234567890
sleep 20 &
sleep 2
kill $!
)

$

In this case the quotes are needed; in other cases it doesn't hurt
to have them.

So here's what I have currently using a Linux system() call in a C
app:

system("display array.png &");
system("sleep 5");
system("kill $!");

Each system() call starts a new shell, so there is no background
command to have generated $!.

system("display array.png & sleep 5; kill $!" );

Clearly there is a problem with my kill syntax since the display never
ends until I manually kill it, at which time I see:

"kill: usage: kill [-s sigspec | -n ...........]"

It seems like I need something like this:

system("kill "$!""); //clearly doesn't work

So, last question, what is the syntax for quotes within quotes? I am
on GNU bash version 2.05a.0(1) i686-pc-linux-gnu [Red Hat 7.3, gcc
2.96]

Escape the quotes (in C or bash):

system("kill \"$!\"");

--
Chris F.A. Johnson, author | <http://cfaj.freeshell.org>
Shell Scripting Recipes: | My code in this post, if any,
A Problem-Solution Approach | is released under the
2005, Apress | GNU General Public Licence
.

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