UNIX for Dummies Questions & Answers

Hi
I have 2 questions:

Q1 - What does
${1:+$1/}*
mean? I guess it lists all files in current directory - Could any one explain how this expression works?

Q2 - I am trying to list directories only in current path - I know that ls could be used but I thought I'd give find a try. I need to list only high level directories (no sub directories or files)

find has option -type d however, the following command always lists sub-directories:

find . -type d

I tried to use maxdepth as in

find . -type d maxdepth 0

but that gives me syntax error.

So my Q2 is:
How to use fiind command to list top level directories only?

Thanks much.

Regarding ${1:+1\}*

In Korn shell you can use expressions such as this to set default values for variables. The above statement checks to see that if $1 (the first input variable) is set, if it is then $1\* is substituted. Can you post the complete line in your script where this is used? Also, there are other builtins, please see the botton of this thread

Regarding listing directories using find. Well thats sort of using a hammer to break an egg Plus, by default, find is recursive in nature. Try using ls | grep ^d or something like that.

Please navigate:
our home page -> Answers to Frequently Asked Questions -> advanced/complex uses of the find command

Above expression is trying to list files (with relative path including paramter passed as first arg ) of the directory passed as argument.
If argument is not passed it lists the files/directories in the current directory.

See below ...

$ cat x.sh
echo ${1:+$1/}*

$ ./x.sh 1234
1234/subdir1 1234/subdir2 1234/subdir3 1234/subdir4 1234/subdir5

$ ls 1234
subdir1 subdir2 subdir3 subdir4 subdir5
$ ./x.sh
1234

Thanks for your help guys.

As per google's inquiry about the context, it appeared in a ksh script that goes through files and directories and does operations on them, it looked like this:

for filename in ${1:+$1/}*; do
....
done

I personlay think that this form of coding in ksh is not comfortable. It is more compact but then again not instantly readable...

Builtins such as that are definitely useful and you will undoubtedly see them again. You may not be too comfortable with them now, but as you learn the language you will find that they provide quite a lot of value. Happy coding.