[jrockway]

Well, my guess is that xargs simply does not accept a filename as the argument. This comes from reading the --help and grepping the manpage for "file".

The point was, when I used "cat file |", I knew it was going to work, and it did. When I tried to eliminate the cat by using the program's built-in ability to read a file, I had to read several manpages before determining that it was not possible. All because some tutorial says "cat is useless", when it clearly saved me much more time than the extra CPU time it used.

And if you are actually asking; xargs is just a utility to read command-line-arguments from stdin. `echo -e "foo\nbar" | xargs rm' === `rm foo; rm bar' (or depending on the xargs implementation; `rm foo bar'). It kind of reminds me of a "functor map" operation, where stdin is a functor (of command-line arguments), and command-line programs are functions. (I will now mention that xargs also does "join" on the "results" of the "function", which is very ... monad-like. But "Monads are teh awesome and everything is one" is my second-least-favorite Internet meme, so I will spare you. :)

[olefoo]

The whole 'useless use of cat' meme is basically designed to let Randal Schwartz make fun of people. At one point it may have made a difference, and certainly if you have a shell script that is getting called 10,000 times a day it might make sense to optimise it. But for doing stuff from the commandline; weird shell acrobatics is a premature optimisation.

[jrockway]

The whole 'useless use of cat' meme is basically designed to let Randal Schwartz make fun of people.

So true.

My requirement for a shell command is that it be reasonably easy to assemble, return something resembling the correct answer, and that it run in a reasonable amount of time.

If your requirements are more strict than those, it's time to write a real program.