Nice easy one! - How do I create an infinite loop??? 1

[JaybOt]

Hi all,

can anyone tell me (or post an example) how i can create an infinite loop? variations welcome.

Sorry for sounding a bit dunce, i have been programming for many years and in many languages but i am new to perl programming and the usual application of commands like 'do/while', 'case', and 'if/then/else' do not seem to work as expected in the shell.

any help would be appreciated!

JayBot
"Always know what you say, but don't always say what you know!"

 

[bartl]

1

    while (1) { print 1; }

2

    for(;;) { print 1; }

3

    {
       print 1;
       redo;
    }

 

[hmerrill]

Slight variation:

while (1) { next; }

better be careful though - that may tie up a lot(or most/all) of your cpu's resources. Would be better to put a sleep in there before the "next".
Hardy Merrill
Mission Critical Linux, Inc.

http://www.missioncriticallinux.com

 

[JaybOt]

Cheers peeps!

Can anyone elaborate a bit more on how i can use these statements in my code?

would this be right...

while (1) {
print 1;
sleep;
do stuf }

while (1) {
print stuff;
sleep;
do stuf
next; }

Jaybot
"Always know what you say, but don't always say what you know!"

 

[hmerrill]

Sorry, when you invoke "sleep" you need to give it the number of seconds you want it to sleep, like

my $ct = 0;
while (1) {
$ct++;
print "$ct\n";
...do stuff...
sleep 5; ### sleeps for 5 seconds
}

That is an infinite loop - to make it stop, you'll either have to kill the process manually, or put a condition in there that will do a "last" or "exit" to break out of the loop.

HTH.
Hardy Merrill
Mission Critical Linux, Inc.

http://www.missioncriticallinux.com

 

[JaybOt]

I have re-writen the above script and it now contins another loop within an 'if' statement. How can i exit this loop, returning control to the original loop.

here is the code (simplified!)

#!/usr/bin/perl
while(1){
if (condition){
do stuff
while(1){
if (condition2){
do more stuff
exit 0
}else{
do nothing but loop2
}
}
}else{
sleep sometime
}
}

the original loop/if works o.k. But the second loop will not exit at the 'exit 0' line. I just want to return to the original loop.

Any idears welcome!

Regards,
JayBot!

"Always know what you say, but don't always say what you know!"

 

[Kiehlster]

I don't know what you want to do but if there's some way that your program can tell if it is done with a loop, then you can do something like this:

#!/usr/bin/perl

$doloop = 1;
$sleeplen = 2;

# loop until $doloop becomes 0
while ($doloop) {
# do stuff
sleep $sleeplen;
if (some condition) {
$doloop = 0;
}
}

This is essentially creating a variable to indicate the status of the program. you could run a test for a specific value of $doloop, and have it loop until it is some value and indicate 0 or some number to be the exit status. This will allow you to also diagnose your program better because you can return a message based on the status value and know where your error was.
Steve Kiehl
webmaster@nanovox.com

http://www.nanovox.com/

 

[stillflame]

also, the command 'last' will exit the innermost loop. "If you think you're too small to make a difference, try spending a night in a closed tent with a mosquito."