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docs: Add argparse examples on how to use the flags

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Fabian Boehm 2024-01-14 10:20:11 +01:00
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commit f8cb8284b2
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17
doc_src/cmds/argparse.rst
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@ -57,13 +57,26 @@ To use this command, pass the option specifications (**OPTION_SPEC**), a mandato
A simple example::
argparse --name=my_function 'h/help' 'n/name=' -- $argv
argparse 'h/help' 'n/name=' -- $argv
or return
If ``$argv`` is empty then there is nothing to parse and ``argparse`` returns zero to indicate success. If ``$argv`` is not empty then it is checked for flags ``-h``, ``--help``, ``-n`` and ``--name``. If they are found they are removed from the arguments and local variables called ``_flag_OPTION`` are set so the script can determine which options were seen. If ``$argv`` doesn't have any errors, like a missing mandatory value for an option, then ``argparse`` exits with a status of zero. Otherwise it writes appropriate error messages to stderr and exits with a status of one.
If ``$argv`` is empty then there is nothing to parse and ``argparse`` returns zero to indicate success. If ``$argv`` is not empty then it is checked for flags ``-h``, ``--help``, ``-n`` and ``--name``. If they are found they are removed from the arguments and local variables called ``_flag_OPTION`` are set so the script can determine which options were seen. If ``$argv`` doesn't have any errors, like an unknown option or a missing mandatory value for an option, then ``argparse`` exits with a status of zero. Otherwise it writes appropriate error messages to stderr and exits with a status of one.
The ``or return`` means that the function returns ``argparse``'s status if it failed, so if it goes on ``argparse`` succeeded.
To use the flags argparse has extracted::
# Checking for _flag_h and _flag_help is equivalent
# We check if it has been given at least once
if set -ql _flag_h
echo "Usage: my_function [-h | --help] [-n | --name=NAME]" >&2
return 1
end
set -l myname somedefault
set -ql _flag_name[1]
and set myname $_flag_name[-1] # here we use the *last* --name=
The ``--`` argument is required. You do not have to include any option specifications or arguments after the ``--`` but you must include the ``--``. For example, this is acceptable::
set -l argv foo