My code for the generation of prime numbers from 2 to a value(given at run time) as fallows is not working. Can you assist me?

Before you do I did it for myself

Why did you exclude the number 2?

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Using code tags is generally better for showing your own code than using quote tags.

When i is 2, that incorrectly excludes it from the list of primes. When i isn't 2, that unnecessarily duplicates work that the inner loop does anyway. Either way, that excess code shouldn't be there.

If you care about performance for moderate to large values of i, using j*j<=i is a better test than j<=i/2.

(I don't know bash scripting very well. So I don't know where the $ is needed in such tests, nor whether there are other syntax difficulties with j*j<=i. I'm commenting just on the language independent algorithm.)

That is wasted work. p would already be 1 whenever that could be executed. Again I don't know the language, but I expect the else is optional, so you could replace all that with just fi.

Is this supposed to be Bash or POSIX sh?

its under bash....

Don't use [ under bash, it's completely deprecated and very dangerous. You really should be using arithmetic expressions $(()) anyway.

And edit your posts to use [code] tags with proper indentation!

Citation needed.

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And why not look up prime numbers generation code on the WEB ? And translate it from whatever procedural language ("C", Perl, Python, etc) into 'bash' if necessary ?

Can be dangerous, yes, if you don't know what you're doing. It can be ok if you've developed habits with [ that work for you. Indeed, for those who are just starting out, [[ is definitely better.

It was mainly the "deprecated" part that I was interested in. For those who are interested, go here.

There's no "can" here. It's just dangerous, plain and simple. Habits don't help you when you make mistakes, and you *will* make a mistake. The *only* advantage [ has is that it's POSIX, and [[ is not. As stated very clearly by that page.

It is very much deprecated, and no well-written bash script uses [. The only reason it exists is for POSIX compatibility.

Wow, calm down man. I would not only disagree with you on the danger, I would disagree on the global statements there.

For one thing, there are hundreds of thousands of scripts (or more) running this way. Like, almost all of them.

For another, I have never seen so much as a single case of this 'worst case' error happening in 20 years of Unix admin.

I see the point they make on that site, but seriously, relax.

And hundreds of thousands of scripts are wrong and are time bombs just waiting for the right trigger to go off. Most people write not-quite-POSIX scripts, not Bash scripts, because it works "good enough" for simple throwaway stuff. If you're writing a Bash script that's supposed to stick around, you should use every feature Bash offers to avoid shooting your leg off. But, that's only for Bash scripting, POSIX scripting is very different.

And I see a case of it at least twice a week on #bash. I suspect you actually have seen a case yourself, you just fix it and move on without realizing it.

Back to the thread...

OP: you might run into problems with variable scope as you have your loops now. You should put for...do...done in {...;} in this case, i.e. { for...do...done; }. Otherwise, p might not be modified for the outer loop.
Kevin Barry