add basic documentation for the config file api
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openwrt/docs/config.txt
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72
openwrt/docs/config.txt
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== Structure of the configuration files ==
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The config files are divided into sections and options/values.
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Every section has a type, but does not necessarily have a name.
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Every option has a name and a value and is assigned to the section
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it was written under.
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Syntax:
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config <type> [<name>] # Section
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option <name> <value> # Option
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Every parameter needs to be a single string and is formatted exactly
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like a parameter for a shell function. The same rules for Quoting and
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special characters also apply, as it is parsed by the shell.
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== Parsing configuration files in custom scripts ==
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To be able to load configuration files, you need to include the common
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functions with:
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. /etc/functions.sh
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Then you can use config_load <name> to load config files. The function
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first checks for <name> as absolute filename and falls back to loading
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it from /etc/config (which is the most common way of using it).
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If you want to use special callbacks for sections and/or options, you
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need to define the following shell functions before running config_load
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(after including /etc/functions.sh):
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config_cb() {
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local type="$1"
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local name="$2"
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# commands to be run for every section
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}
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option_cb() {
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# commands to be run for every option
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}
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You can also alter option_cb from config_cb based on the section type.
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This allows you to process every single config section based on its type
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individually.
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config_cb is run every time a new section starts (before options are being
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processed). You can access the last section through the CONFIG_SECTION
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variable. Also an extra call to config_cb (without a new section) is generated
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after config_load is done.
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That allows you to process sections both before and after all options were
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processed.
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You can access already processed options with the config_get command
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Syntax:
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config_get <section> <option> # prints the value of the option
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config_get <variable> <section> <option> # stores the value inside the variable
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In busybox ash the three-option config_get is faster, because it does not
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result in an extra fork, so it is the preferred way.
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Additionally you can also modify or add options to sections by using the
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config_set command.
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Syntax:
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config_set <section> <option> <value>
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