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<title>6.21.1.2 What are options for?
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<H3><A NAME=
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6.21.1.2 What are options for?
Options are used to provide extra information to tune or customize the
execution of a program. In case it wasn't clear, options are usually
<em>optional
</em>. A program should be able to run just fine with no options
whatsoever. (Pick a random program from the
<span class=
"Unix">Unix
</span> or GNU toolsets. Can
it run without any options at all and still make sense? The main
exceptions are
<code>find
</code>,
<code>tar
</code>, and
<code>dd
</code>--all of which are mutant
oddballs that have been rightly criticized for their non-standard syntax
and confusing interfaces.)
Lots of people want their programs to have ``required options''. Think
about it. If it's required, then it's
<em>not optional
</em>! If there is a
piece of information that your program absolutely requires in order to
run successfully, that's what positional arguments are for.
As an example of good command-line interface design, consider the humble
<code>cp
</code> utility, for copying files. It doesn't make much sense to try to
copy files without supplying a destination and at least one source.
Hence,
<code>cp
</code> fails if you run it with no arguments. However, it has a
flexible, useful syntax that does not require any options at all:
<div class=
"verbatim"><pre>
You can get pretty far with just that. Most
<code>cp
</code> implementations
provide a bunch of options to tweak exactly how the files are copied:
you can preserve mode and modification time, avoid following symlinks,
ask before clobbering existing files, etc. But none of this distracts
from the core mission of
<code>cp
</code>, which is to copy either one file to
another, or several files to another directory.
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<span class=
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2005.
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