Shell Programming and Scripting

Hi,

I am facing issues with test condition. I had a compound condition to write for both if and while,

In one of the texts i referred, with a korn shell we can write compound statements like: [[condition1 || condition 2 ]], however this doesn't worked for me. For example:

if [[ "$go_2_it" == "Y" || "$go_2_it" == "y" ]] doesn't works, but
if [ "$go_2_it" = "Y" ] || [ "$go_2_it" = "y" ] worked.

Now, similarly in a while loop I have something like,

while [[ "$go_2_it" != "Y" || "$go_2_it"t != "y" || "$go_2_it" != "N" || "$go_2_it" != "n" ]] or

while [ "$go_2_it" != "Y" ] || [ "$go_2_it" != "y" ] || [ "$go_2_it" != "N" ] || [ "$go_2_it" != "n" ]

None of the above works, do not understand why.

Also, if anybody can suggest whats [[ ]], and does it behaves differently than []. In the text, I referred, it says [[]] is for korn and [] is for bash. I am working with korn shell, but [[]] doesn't help me.

Thanks

Hello,
it may not be much of a comfort but both Your versions of while loop conditions worked on my machine, in both bash (3.2) and ksh (93s) on Linux.

As in

Code:

while [[ "$go_2_it" != "Y"  ||  "$go_2_it" != "y"  ||  "$go_2_it" != "N"  ||  "$go_2_it" != "n" ]];  do echo hey; done

or

Code:

while [ "$go_2_it" != "Y" ] || [ "$go_2_it" != "y" ] || [ "$go_2_it" != "N" ] || [ "$go_2_it" != "n" ];  do echo hey; done

I am not sure but I think the single [ is actually a command, equal or similar to the test command, but [[ is a grouping mechanism and has different rules for wildcard and variable expansion. I guess You should Google on it. I have used both and not sure why I did it, maybe just because an example I had to build from used either and it worked so I never really bothered.

/Lakris