while {some command does not exit = 1)

while {some command does not exit = 1)

[TJ Luoma]

I keep thinking that there must be an easier way to do this, but I
can't figure out what it would be, and Google has not helped.

I'm trying to create a "while" loop which will keep going as long as
some command does not exit = 0

Here's what I have been doing:

#!/bin/zsh -f

EXIT=1

while [ "$EXIT" = "1" ]
do

	drutil discinfo | fgrep -q 'Please insert a disc to get disc info.'

	EXIT="$?"

	FOO

done

exit 0
# EOF

(where 'FOO' is some command I want to run)

What I keep thinking I ought to be able to do is something like this

while ((! drutil discinfo | fgrep -q 'Please insert a disc to get disc info.' ))
do

	FOO


done

I realize that "while (( ))" syntax is wrong, but I hope the idea is
clear. It appears that the | might be what is making this not work.

Is there an easier way to do this?

TjL

Re: while {some command does not exit = 1)

[Bart Schaefer]

[-- Attachment #1: Type: text/plain, Size: 821 bytes --]

On Sun, Jun 2, 2013 at 9:24 PM, TJ Luoma <luomat@gmail.com> wrote:

> Here's what I have been doing:
>
> #!/bin/zsh -f
>
> EXIT=1
>
> while [ "$EXIT" = "1" ]
> do
>
>         drutil discinfo | fgrep -q 'Please insert a disc to get disc info.'
>
>         EXIT="$?"
>
>         FOO
>
> done
>

It should work to just write

while ! drutil discinfo | fgrep -q 'Please insert a disc to get disc info.'
do
    FOO
done

Except that the $? value of the pipeline is going to be the exit status of
fgrep, not of drutil.  I suspect that's what you meant, so FOO runs only
when a disc is present.  You can make this clearer by writing it as

while ! { drutil discinfo | fgrep -q 'Please insert a disc to get disc
info.' }
do
    FOO
done

Spaces around the "!" are important, especially if you're in a shell with
history enabled.