Homework & Coursework Questions

Code:

[root@dell ~]# x=A
[root@dell ~]# [ $x = [aA] ] && echo "Add" 
[root@dell ~]# [ $x == [aA] ] && echo "Add" 
[root@dell ~]# [[ $x = [aA] ]] && echo "Add" 
Add
[root@dell ~]# [[ $x == [aA] ]] && echo "Add" 
Add
[root@dell ~]# echo $SHELL
/bin/bash

However:

Code:

[root@dell ~]# x=A
[root@dell ~]# x=${x,,}
[root@dell ~]# [ $x = a ] && echo "Add"
Add
[root@dell ~]#

So yes, for the REGEX you need the double brackets.
BTW: bad behaviour example as i was running it as root

Edit: Yes, for anything more complex than a simple single yes/no requires a standard if-statement like:

Code:

if [ $x -ge 100 ] || [[ "$x" == [aA] ]]
then    echo "Great"
else    echo "Low"
fi

BTW: The only 'place' i actualy use == (as it wont work properly with a single) is with PHP.
All of both the shells (sh,bash) i came across worked well with a single =.

EDIT2:
Just read (once more) the 'man bash', and beeing in the homework section i must say:
-> Better get used to use the proper syntax right from the start!