48 lines
2.0 KiB
ReStructuredText
48 lines
2.0 KiB
ReStructuredText
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.. index:: Format Strings
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.. _format-strings:
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Format Strings
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--------------
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libxo uses format strings to control the rendering of data into the
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various output styles. Each format string contains a set of zero or
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more field descriptions, which describe independent data fields. Each
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field description contains a set of modifiers, a content string, and
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zero, one, or two format descriptors. The modifiers tell libxo what
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the field is and how to treat it, while the format descriptors are
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formatting instructions using printf-style format strings, telling
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libxo how to format the field. The field description is placed inside
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a set of braces, with a colon (":") after the modifiers and a slash
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("/") before each format descriptors. Text may be intermixed with
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field descriptions within the format string.
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The field description is given as follows::
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'{' [ role | modifier ]* [',' long-names ]* ':' [ content ]
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[ '/' field-format [ '/' encoding-format ]] '}'
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The role describes the function of the field, while the modifiers
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enable optional behaviors. The contents, field-format, and
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encoding-format are used in varying ways, based on the role. These
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are described in the following sections.
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In the following example, three field descriptors appear. The first
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is a padding field containing three spaces of padding, the second is a
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label ("In stock"), and the third is a value field ("in-stock"). The
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in-stock field has a "%u" format that will parse the next argument
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passed to the xo_emit function as an unsigned integer::
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xo_emit("{P: }{Lwc:In stock}{:in-stock/%u}\n", 65);
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This single line of code can generate text (" In stock: 65\n"), XML
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("<in-stock>65</in-stock>"), JSON ('"in-stock": 6'), or HTML (too
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lengthy to be listed here).
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While roles and modifiers typically use single character for brevity,
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there are alternative names for each which allow more verbose
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formatting strings. These names must be preceded by a comma, and may
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follow any single-character values::
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xo_emit("{L,white,colon:In stock}{,key:in-stock/%u}\n", 65);
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