Re: [Help-bash] Simple echo is printing the wrong value

[Greg Wooledge]

On Wed, Apr 04, 2012 at 11:29:47AM -0600, Bill Gradwohl wrote:
> With 2 files in the directory, one named * and the other named nonAsterisk,
> the for loop:
> for file in *; do
> produces file='*' on the first pass.
> The echo statement contains the unquoted $file which bash expands to 2
> parameters namely * and nonAsterisk.
> 
> Same goes for the func line.
> 
> Therefore these 2 statements get 2 passed parameters which is what I
> wanted, and got.
> 
> Am I right so far?

Yes, $file would expand to two words (and therefore two arguments in the
appropriate contexts) on the iteration where file=*.

But I do have a problem with "which is what I wanted", because it is
inconceivable that you could want this behavior.  See below.

> If so, then quoting is still optional isn't it?

"for file in *" should be processing one file per iteration.  Quoting
"$file" is mandatory.  If you don't quote it, you could split a single
filename into multiple arguments, or expand glob characters in a filename
and produce a whole crapload of arguments.

for file in *; do
   process $file      # Wrong.  You will end up passing the wrong args.
done

for file in *; do
   process "$file"    # Right.
done

Putting a filename into a string variable and then failing to quote that
variable when expanded is NEVER correct.

If your actual code is not "for file in * ..." but rather something like
"exts='*.png *.jpg *.gif'; for file in $exts ..." then that is a totally
different case, but you STILL have to quote "$file" even if you don't
quote $exts.

Side note: exts='*.png *.jpg *.gif' is a Bourne-shell-ism that should
not be used in Bash.  Storing lists of things in a string variable with
spaces in between them is a hack to be used only in languages that do
not have arrays.  Bash has arrays.  But it's the only example I can come
up with that even resembles your remarks.

Side side note: when producing an example that demonstrates a problem,
don't mangle the original code so much that the example is no longer
relevant or descriptive.