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Re: Question about coreutils common option "-"


Peter Farley wrote:

> I thought the following would produce "ls -l" output
> for the space-separated list of files selected by the
> "find" options, but instead I get an error message
> from "ls":
> 
> $ find a -daystart -type f -mtime 7 -printf " %p"|ls
> -l -
> ls: -: No such file or directory
> 
> The output from the "find" looks like this:
> 
> $ find a -daystart -type f -mtime 7 -printf " %p"
>  a/list.txt a/list_0002.txt

I've never heard of using '-' to ls this way.  The coreutils info page
does list it as a common flag, but my interpretation of the language
there is that it's only referring to programs that act as input/output
filters, not as a general-purpose way of passing filename arguments. 
That's why xargs exists.

You can get ls-like output from find without any other programs:

find a -daystart -type f -mtime 7 -ls

If you must use an external program, the usual way to take the output
from find and send it as arguments is with xargs:

find a -daystart -type f -mtime 7 | xargs ls -l

Note that both this and your '-printf " %p"' method will not work for
filenames that contain spaces or special characters.  Therefore the
superior way of doing this is:

find a -daystart -type f -mtime 7 -print0 | xargs -0 ls -l

> I do not have an *ix system on which to test if this
> is a Cygwin coreutils problem or a misunderstanding by
> me of the operation of the "-" option.  Can you please
> tell me if I am wrong about my use of the "-" option?

It doesn't work under linux either.  (It's the same coreutils code in
either case.)

Brian

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