Re: what should xargs do with empty stdin?

From: Todd Smith (tsmith_at_sgi.com)
Date: 01/03/04

  • Next message: Erik Max Francis: "Re: what should xargs do with empty stdin?" 
    Date: 2 Jan 2004 23:44:01 GMT

    In article <3FF5E99C.BFD8D794@alcyone.com>, Erik Max Francis <max@alcyone.com> writes:
    |> Todd Smith wrote:
    |>
    |> > Say I write a sequence of commands to remove all C source files under
    |> > a particular root directory. If there happen not to be any such files
    |> > there, I get the following (unnecessary and annoying) error:
    |> >
    |> > > find . -name "*.[ch]" -print | xargs rm
    |> > Incorrect usage
    |> > Usage: rm [-fir] file ...
    |> ...
    |> > Is this the intended behavior? Is there a portable way of avoiding
    |> > this? On IRIX, I can use "xargs -L1", but the (GNU?) xargs on my
    |> > Linux system doesn't like -L or seem to have anything equivalent.
    |>
    |> Look at the error: It's _rm_ reporting this complaint, not xargs. Your
    |> question actually has nothing to do with xargs; it's how to get the
    |> command that xargs is going to run to accept no arguments. With rm, add
    |> the -f option.

    I understand that it is _rm_ reporting the complaint, but I think its
    complaint is justified.

    Certainly this behavior of xargs violates the principle of least
    surprise. If I ran the following in csh:

        foreach i (*.[ch])
            # loop body
        end

    in a directory with no C source files, I definitely wouldn't expect
    the loop body to still be executed once, with no value for $i, even if
    I could find some way (like adding a -f option to _rm_) to make it
    work.

    Some commands have different modes of operation, depending upon the
    presence or absence of arguments. Some uses of xargs specify a
    command *and* some initial arguments, to be followed by sets of
    arguments added by xargs. I would rather have xargs behave
    intuitively than have to go and ensure that each one of the
    (unlimited) set of command possibilities I might use with it is able
    to handle this boundary case gracefully.

    In any case, another poster pointed me to an appropriate option for
    GNU xargs, so at least I am able to get the behavior I wanted, if not
    in the same way for every platform's default xargs implementation.

    Todd Smith

  • Next message: Erik Max Francis: "Re: what should xargs do with empty stdin?"

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