Shell Programming and Scripting

Then search for anything containing a character which is not any of those.

Code:

case $b in *[!/-_A-Za-z0-9]*) echo error >&2;; esac

Thanks a lot for helping. I will try out all the proposed solution and update you.

I wrote the code as follows. I purposely create an infinite loop to re-enter the directory:

while :
do
echo "Enter directory: \c"
read b
case $b in
*[!/-_A-Za-z0-9]*) echo "Error" >&2;;
*[!/-_A-Za-z0-9]) echo "Error 1" >&2;; # For experiment only
[!/-_A-Za-z0-9]*) echo "Error 2" >&2;; # For experiment only
[!/-_A-Za-z0-9]) echo "Error 3" >&2;; # For experiment only
esac
done

The result looks unpredictible to me. The ones with wrong result is indicated by "[Wrong]". They either fail to detect special character or treat valid ones as invalid. See the output below:

Enter directory: 12@ [Wrong]
Enter directory: 12@12 [Wrong]
Enter directory: 12#3]
Error
Enter directory: 12`76
Error
Enter directory: 12\87 [Wrong]
Enter directory: 12/778
Enter directory: 12%87
Error
Enter directory: 67)
Error
Enter directory: *(&*
Error
Enter directory: !76h
Error
Enter directory: (12
Error
Enter directory: `344
Error
Enter directory: 788'
Error
Enter directory: 87"+=
Error
Enter directory: 12_767
Enter directory: 788- [Wrong]
Error
Enter directory: 67-878 [Wrong]
Error
Enter directory: :78 [Wrong]
Enter directory: 878; [Wrong]
Enter directory: gha.js
Error
Enter directory: hg.
Error
Enter directory: |78
Error
Enter directory: {98}^H
Error

sed method does not seem to work either:

> echo 'ab!cada' | sed -n -e "s+^[a-zA-Z0-9/_\-]*$+&+p"
cada: Event not found.
> echo 'ab21212cada' | sed -n -e "s+^[a-zA-Z0-9/_\-]*$+&+p"
Illegal variable name.
> echo 'ab2121/2cada' | sed -n -e "s+^[a-zA-Z0-9/_\-]*$+&+p"
Illegal variable name.
> echo 'ab2-_121/2cada' | sed -n -e "s+^[a-zA-Z0-9/_\-]*$+&+p"
Illegal variable name.

Please post the output of uname -a

> uname -a
SunOS dsu1a 5.9 Generic_118558-19 sun4u sparc SUNW,Netra-240

The case statement works for me in bash.

You could try using caret ^ instead of exclamation mark ! to signify "not" in the character class, although I would be mildly surprised if that works.