From mboxrd@z Thu Jan  1 00:00:00 1970
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
In-reply-to: Your message of "Sun, 04 Oct 2009 03:03:27 +1100."
	<20091003160327.GA15021@nipl.net>
References: <20091003160327.GA15021@nipl.net>
From: Bakul Shah <bakul+plan9@bitblocks.com>
Date: Sat,  3 Oct 2009 11:46:16 -0700
Message-Id: <20091003184617.14C075B2E@mail.bitblocks.com>
Subject: Re: [9fans] mishandling empty lists - let's fix it
Topicbox-Message-UUID: 7ceefd4a-ead5-11e9-9d60-3106f5b1d025

On Sun, 04 Oct 2009 03:03:27 +1100 Sam Watkins <sam@nipl.net>  wrote:
>
>   find -name '*.c' | xargs cat | cc -     # this clever cc can handle it :)
>
> This program works fine until there are no .c files to be found, in that case
> it hangs, waiting for one on stdin!  This is a hazard to shell scripters, and
> a potential source of security holes.

Your example doesn't hang (and if it does, your xargs is
broken).  You are thinking of something like this:

$ echo 'cat $*' > foo.sh
$ sh foo.sh

This is not elegant but a reasonable tradeoff.  A common use
of many tools is in a pipeline and having to type - every
time can get annoying.

To "fix" this you may think of changing your shell to append
/dev/null if a command is given no arguments but that will
fail in cases like `cat -v'.  In unix it is upto each command
to interprets its arguments and a shell can not assume
anything about command arguments.