UNIX for Dummies Questions & Answers

Hi,

I am writing a BASH shell script. I would like to count all the files in the CURRENT directory matching a specific pattern. Could someone suggest the best/simplest way to do this. I have thought of these solutions (for simplicity the pattern is all files starting with A):

ls -1 *A | wc -l

OR

find ./ -name "A*" | wc -l

The problem with the first solution is that it returns an error message if there are no files that match the pattern. If this is the case I just want 0 returned.

The problem with the second solution is that it searches the current directory, but also any sub-directories included within.

Any suggestions? Thanks a lot.

Mike

Code:

>ls -1 A* 2>/dev/null | wc -l
0

Where I redirect error output to a location that I do not care about. This is a common way of skipping past error messages.

You might also incorporate this into find commands when searching for a file (not necessarily this example), but to avoid the errors telling you that you do not have rights to view a directory.

By the way, the -1 is not necessary in this example. I included it above since I was only trying to show the error redirect. The better command is

Code:

>ls A* 2>/dev/null | wc -l

Code:

$ touch A{1..5} B{1..7}
$ ls
A1  A2  A3  A4  A5  B1  B2  B3  B4  B5  B6  B7
$ shopt -s nullglob 
$ f=(A*)
$ echo ${#f[@]}
5
$ f=(C*)
$ echo ${#f[@]}
0

Thank you for the suggestions. I have read about /dev/null but have never tried doing that. What happens to output when you redirect it there. Does it go into obscurity or so you have to "purge" /dev/null sometimes. Is it a file that you can open up and view its contents?

Mike

No need to cleanup /dev/null
in fact, do the following

Code:

> ls -l /dev/n*

Kind of strange the entry for null... Not like any normal file.

Yes,
character special:

Code:

% file /dev/null
/dev/null: character special