N00b: Simple Question about Bash Func and Vars:

TylerD75 · 04-03-2005, 04:35 AM

Hi!
I'm kind of a n00b at bash scripting (read: long time since my last bash script), and have a (probably) simple Q:

I've made a script with some functions but I'm unable to catch their return value...
Example:
------------------------------------------------------
getNumInst() {
ps auxww | grep azureus | while read OUTP1
do
let "i+=1"
nrInst=$i
done
return $nrInst
}

instances=$(getNumInst)
echo "Instances of Azureus: $instances"
-------------------------------------------------------
Before you ask why I do this as a function: I've also tried it as a simple while loop, but with the same result.

I guess its got something to do with integer values in strings, or something...
But the strange thing is that if I put an echo "Count: $nrInt" before "done", it will show the current value of $nrInst. But if I put it after done, there's no value (as in "" or null). I've also tried "declare nrInst" and "declare -i i" without a positive result...
So what am I doing wrong? Can someone please help me with this?

PS! I'm trying to write this because every now and then Azureus shuts down, and I don't want to check it and restart it every time it happens...

slakmagik · 04-03-2005, 04:39 AM

Would this do?

[ j@fulltiltboogie ][ 04-03 05:39 ][ ~ ]
:nrInstances=`ps auxww | grep kdeinit | wc -l`

[ j@fulltiltboogie ][ 04-03 05:40 ][ ~ ]
:echo $nrInstances
24

Not sure what's wrong with the first example and this seemed easier than figuring it out.

jlliagre · 04-03-2005, 04:58 AM

In your original script, replace "return" by "echo" and it works.
Return if for returning a numerical status: 0=OK, other=error code.

perfect_circle · 04-03-2005, 05:13 AM

Code:

getNumInst() {
    ps auxww | grep azureus | while read OUTP1
    do
        let "i+=1"
        nrInst=$i
    done
    return $nrInst
}

instances=$(getNumInst)
echo "Instances of Azureus: $instances"

This is wrong. This looks like C. Not bash. This is not the way functions return values in bash.

In bash the returning value is stored in the special variable "$?"

SO instead of this:

Code:

instances=$(getNumInst)
echo "Instances of Azureus: $instances"

Try this:

Code:

getNumInst
instances=$?
echo "Instances of Azureus: $instances"

Also when I declare a function I put the reserved word function in the beginning:
function getNumInst() {.......................

but this is optional i think....

TylerD75 · 04-03-2005, 05:15 AM

Thanks for the quick reply!
Oops! I read about that too... Lol I've been up too late I think!

I'll try that new solution!

TylerD75 · 04-03-2005, 05:22 AM

Thanks M8! That did solve my problem! And thanks to the first reply as well! It did simplify my solution!

TylerD75 · 04-03-2005, 06:03 AM

Another related question:
Is it at all possible to return a string from a function?

Update:
Never mind that last Q, Jlliagre solved it for me!!
Thanks again!