Re: pathname expansion part two

[Bob Proulx]

javajo91 wrote:
> "For example, if you wanted to list all of the files in the directories /usr
> and usr2, you could type ls /usr*.

Because the '*' is a file glob.  It is called a glob because it
matches a glob of characters.  The process of the expansion is called
globbing.  "/usr*" matches "/usr" and "/usr2" both.  That is expanded
on the command line.

  $ ls /usr*

is the same as

  $ ls /usr /usr2

The ls command never sees a '*' because the shell expands it first.
You can use echo to see what the shell has expanded.

  $ echo foo /usr*
  foo /usr /usr2

> If you were only interested in the files
> beginning with the letters b and e in these directories, you could type ls
> /usr*/[be]* to list them." 

The /usr* matches and expands to /usr /usr2 and then the [be]* matches
"bin" and "etc".  The result is the same as

  $ ls /usr/bin /usr/etc

And so the contents of those directories are listed.  Again you can
see this using echo.  [Most people won't have a /usr/etc on their
system though and so that would not expand for them.]

  $ echo foo /usr*/[be]*
  /usr/bin /usr/etc

> When i type /usr*/[be]* i do not get all the files within /usr that begin
> with a b or an e but instead get ALL the files within /usr/bin and /usr/etc.

Because you are asking ls to list those directories they are being
listed for you.  If you want to ask ls to list the directory arguments
as a file instead of as a directory then you can add the -d option.
(But it is almost the same as echo in that case.)

  $ ls /usr*/[be]*
  ...contents of /usr/bin and /usr/etc...

  $ ls -d /usr*/[be]*
  /usr/bin     /usr/etc

Also remember that directories are simply files in a Unix filesystem.
They are special files and have special properties but files just the
same.

Bob