simple grep in a shell script

[sandeep t]

I have a following shell script on Linux 64bit machine.

If [ `uname -a | grep 64` ]
then
echo 64bit
fi

The above script doesn't work properly. Why?
Also, the following script works fine. What's the difference?

if [ `uname | grep Linux` ]
then
echo Linux
fi

[ghostdog74]

capital If?

[sandeep t]

Sorry, that was a typo while writing here.. It is 'if'

[khafa]

post the error you get when you run the script

[i92guboj]

The key is in the output.

This:

uname -a | grep 64

produces an output which contains spaces, so, if will complain that there are too many arguments. Quoting when working with strings is a good thing to do.

On the contrary:

uname | grep Linux

This other command produces a single word as output. So, it will work even if you don't quote it correctly. In any case, it wouldn't hurt either to quote it. So, let's modify the code this way:

If [ "`uname -a | grep 64`" ]
then
echo 64bit
fi

However, I think that you should be parsing "uname -m" instead. There are lots of ways that a 64 could appear even if you are not using a 64 bits kernel so "uname -m" might be more accurate. It should say "x86_64".

[i92guboj]

Please, delete this post, I posted the same thing twice by accident. Sorry.

[sandeep t]

Great!
Thanks, This is the reply I was expecting..