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af793c49f3
It is better to have docs built in the repo so that building scm version doesn't fail with 'missing doc directory' error.
116 lines
2.1 KiB
Plaintext
116 lines
2.1 KiB
Plaintext
Default values
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==============
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For elements such as arguments and options, if ``default`` property is set, its value is stored in case the element was not used.
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.. code-block:: lua
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:linenos:
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parser:option("-o --output", "Output file.", "a.out")
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-- Equivalent:
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parser:option "-o" "--output"
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:description "Output file."
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:default "a.out"
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::
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$ lua script.lua
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.. code-block:: lua
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{
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output = "a.out"
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}
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The existence of a default value is reflected in help message, unless ``show_default`` property is set to ``false``.
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::
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$ lua script.lua --help
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::
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Usage: script.lua [-o <output>] [-h]
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Options:
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-o <output>, --output <output>
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Output file. (default: a.out)
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-h, --help Show this help message and exit.
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Note that invocation without required arguments is still an error.
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::
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$ lua script.lua -o
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::
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Usage: script.lua [-o <output>] [-h]
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Error: too few arguments
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Default mode
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------------
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``defmode`` property regulates how argparse should use the default value of an element.
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If ``defmode`` contains ``u`` (for unused), the default value will be automatically passed to the element if it was not invoked at all. This is the default behavior.
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If ``defmode`` contains ``a`` (for argument), the default value will be automatically passed to the element if not enough arguments were passed, or not enough invocations were made.
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Consider the difference:
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.. code-block:: lua
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:linenos:
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parser:option "-o"
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:default "a.out"
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parser:option "-p"
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:default "password"
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:defmode "arg"
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::
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$ lua script.lua -h
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::
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Usage: script.lua [-o <o>] [-p [<p>]] [-h]
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Options:
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-o <o> default: a.out
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-p [<p>] default: password
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-h, --help Show this help message and exit.
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::
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$ lua script.lua
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.. code-block:: lua
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{
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o = "a.out"
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}
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::
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$ lua script.lua -p
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.. code-block:: lua
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{
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o = "a.out",
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p = "password"
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}
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::
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$ lua script.lua -o
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::
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Usage: script.lua [-o <o>] [-p [<p>]] [-h]
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Error: too few arguments
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