forked from lda/telodendria
112 lines
3.3 KiB
Groff
112 lines
3.3 KiB
Groff
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.Dd $Mdocdate: March 12 2023 $
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.Dt JSON 1
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.Os Telodendria Project
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.Sh NAME
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.Nm json
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.Nd A simple command line utility for parsing and generating JSON.
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.Sh SYNOPSIS
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.Nm
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.Op Fl s Ar query
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.Op Fl e Ar str
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.Sh DESCRIPTION
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.Nm
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is a simple command line utility for dealing with JSON. It is
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somewhat inspired by
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.Xr jq 1 ,
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but is not compatible in any way with it.
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.Nm
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is designed to be much simpler than
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.Xr jq 1 ,
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and is built on Telodendria's own
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.Xr Json 3
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API. It primarily exists to ease development of Telodendria, and
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to make development possible without having to install any external
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tools.
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.Pp
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The options are as follows. Unless stated otherwise, these options
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are mutually exclusive, and the last one specified takes precedence.
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All positional parameters are ignored.
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.Bl -tag -width Ds
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.It Fl s Ar query
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Use
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.Va query
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to query a field from a JSON object given on the standard input.
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The query syntax very vaguely resembles C code, but it is much
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more primitive. Multiple queries are separated by an arrow
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(``->''). This makes it trivial to drill down into nested
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objects and arrays.
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.Pp
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To select a value from an object, just specify the key. To select
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an element from an array specify the key whose value is the array,
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and then use the C square bracket syntax to select an element.
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.Pp
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A number of ``functions'' exist to make
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.Nm
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more versatile. Functions are called by prefacing the key with
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a ``@'' symbol. Functions can appear anywhere in the query, provided
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they make sense within the context of the JSON object being processed.
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The available functions are as follows:
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.Bl -tag -width Ds
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.It keys
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When applied to an object, outputs an array of keys.
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.It length
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When applied to an array, outputs the number of elements in the
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array. When applied to a string, returns the number of bytes
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needed to store the decoded version of the string.
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.It decode
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When applied to a string, outputs the decoded version of the
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string.
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.El
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.Pp
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When a key is prefaced with the ``^'' symbol, then instead of getting
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the value at that key, it is removed from the object, and the new
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object is passed along.
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.It Fl e Ar str
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Encode
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.Va str
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as a JSON string and print it to standard output. This is useful for
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generating JSON with shell scripts.
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.El
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.Pp
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If no options are specified, then the default behavior of
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.Nm
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is to read a JSON object given on the standard input and pretty-print
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it to the standard output, or print an error to standard error if
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the given input is invalid.
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.Sh EXAMPLES
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.Pp
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Get the error string of an error returned by a Matrix API endpoint:
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.Bd -literal -offset indent
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json -s 'error->@decode'
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.Ed
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.Pp
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Get the number of stages in the first flow listed in a list
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of user-interactive authentication flows:
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.Bd -literal -offset indent
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json -s 'flows[0]->stages->@length'
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.Ed
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.Pp
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Get the first stage of the first flow listed in a list
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of user-interactive authentication flows:
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.Bd -literal -offset indent
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json -s 'flows[0]->stages[0]->@decode'
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.Ed
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.Pp
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List the keys in a JSON object:
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.Bd -literal -offset indent
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json -s '@keys'
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.Ed
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.Pp
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Get the number of keys in a JSON object:
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.Bd -literal -offset indent
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json -s '@keys->@length'
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.Ed
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.Sh EXIT STATUS
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.Nm
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exits with
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.Va EXIT_SUCCESS
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if all command line options were valid and the given JSON object
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parses successfully. It exits with
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.Va EXIT_FAILURE
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in all other scenarios.
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