Shell Programming and Scripting

Hi,
how to write an if statement for values in between

if [$? -ne 0];then

fi

here I want to write an if statement if $? is inbetween 1 and 126
how to write this
if [$? inbetween 1 and 126];then
fi


I'd also like to know the difference between the following two if statements
if [$? -ne 0];then
fi
and
if [[$? -ne 0]];then
fi
Thanks for your time.
Ram

Depends on which shell you are using. The "[" version of test is the original one and tends to be an external program. Newer shells have "[[" which is a built in one and thus more efficient. You might also have "((" which is specifically for numeric stuff which means that you can use normal numeric comparisons rather than -ne, -eq etc.

To do an "in between" test with any of the above you need to use AND or OR depending on which way round you do it. AND is && and OR is ||


e.g.

if [ $val -lt 127 ] && [ $val -gt 0 ]
then
......

fi



there might be niftier ways with some shells (like doing the && or || inside a single test ) but it depends what you are using.

For the in-between question:

if [ $? -ge 1 -a $? -le 126 ] ; then
...
fi


For the what's the difference question:
I'm kinda curious about that too.

We were posting at the same time.


Hmmm... I was curious about those double ampersands and pipes I've seen as well.

Thanks.

This is the Bourne shell syntax:

Code:

[ condition1 -a condition2 ]
[ condition1 -o condition2 ]

And this is the Korn shell syntax:

Code:

[[ condition1 && condition2 ]]
[[ condition1 || condition2 ]]

The -a and -o clauses can not be used inside the Korn shell-specific test statement.

Regards

Oh. I get it. Kinda. Just another way to confuse us.

Thanks for the info (except I thought I'm using the Korn shell...)

The Bourne syntax is still valid in Korn, but not vice versa. In other words, Korn shell is backwards-compatible with the "classic" Bourne shell.

Just for completeness, [ test1 ] && [ test2 ] is valid Bourne syntax too.