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| .\" # | ||
| .\" # Copyright (c) 2021, Juniper Networks, Inc. | ||
| .\" # All rights reserved. | ||
| .\" # This SOFTWARE is licensed under the LICENSE provided in the | ||
| .\" # ../Copyright file. By downloading, installing, copying, or | ||
| .\" # using the SOFTWARE, you agree to be bound by the terms of that | ||
| .\" # LICENSE. | ||
| .\" # Phil Shafer, May 2021 | ||
| .\" | ||
| .Dd May 13, 2021 | ||
| .Dt LIBXO-CSV 7 | ||
| .Os | ||
| .Sh NAME | ||
| .Nm --libxo encoder=csv[+options] | ||
| .Nd a CVS encoder for libxo\-based commands | ||
| .Sh DESCRIPTION | ||
| The | ||
| .Nm libxo | ||
| library supports a "pluggable" encoder mechanism, and ships with an | ||
| encoder for CSV (comma separated values) files. The encoder allows | ||
| paths and fields to be selected out of the output contents: | ||
| .Bd -literal -offset indent | ||
| % df --libxo @csv | ||
| name,total-blocks,used-blocks,available-blocks,used-percent,mounted-on | ||
| zroot/ROOT/default,3825984331,29376725,3796607605,1,/ | ||
| devfs,1,1,0,100,/dev | ||
| zroot/usr/home,3808301289,11693684,3796607605,0,/usr/home | ||
| zroot/var/audit,3796607806,201,3796607605,0,/var/audit | ||
| ... | ||
| % df --libxo @csv+leafs=name.used-percent | ||
| name,used-percent | ||
| zroot/ROOT/default,1 | ||
| devfs,100 | ||
| zroot/usr/home,0 | ||
| zroot/var/audit,0 | ||
| ... | ||
| % df --libxo @csv+leafs=available-blocks+no-header / | ||
| 3796607605 | ||
| .Ed | ||
| contains software to generate four "built-in" | ||
| formats: text, XML, JSON, and HTML. | ||
| These formats are common and useful, but there are other common and | ||
| useful formats that users will want, and including them all in the | ||
| libxo software would be difficult and cumbersome. | ||
| .Pp | ||
| To allow support for additional encodings, libxo includes a | ||
| "pluggable" extension mechanism for dynamically loading new encoders. | ||
| .Nm libxo -based | ||
| applications can automatically use any installed encoder. | ||
| .Pp | ||
| Use the "encoder=XXX" option to access encoders. The following | ||
| example uses the "cbor" encoder, saving the output into a file: | ||
| .Bd -literal -offset indent | ||
| df --libxo encoder=cbor > df-output.cbor | ||
| .Ed | ||
| .Pp | ||
| Encoders can support specific options that can be accessed by | ||
| following the encoder name with a colon (':') or a plus sign ('+') and | ||
| one of more options, separated by the same character: | ||
| .Bd -literal -offset indent | ||
| df --libxo encoder=csv+path=filesystem+leaf=name+no-header | ||
| df --libxo encoder=csv:path=filesystem:leaf=name:no-header | ||
| .Ed | ||
| .Pp | ||
| These examples instructs libxo to load the "csv" encoder and pass the | ||
| following options: | ||
| .Bd -literal -offset indent | ||
| path=filesystem | ||
| leaf=name | ||
| no-header | ||
| .Ed | ||
| .Pp | ||
| Each of these option is interpreted by the encoder, and all such | ||
| options names and semantics are specific to the particular encoder. | ||
| Refer to the intended encoder for documentation on its options. | ||
| .Pp | ||
| The string "@" can be used in place of the string "encoder=". | ||
| .Bd -literal -offset indent | ||
| df --libxo @csv:no-header | ||
| .Ed | ||
| .Sh The CSV (Comma Separated Values) Encoder | ||
| .Nm libxo | ||
| ships with a custom encoder for "CSV" files, a common format for | ||
| comma separated values. The output of the CSV encoder can be loaded | ||
| directly into spreadsheets or similar applications. | ||
| .Pp | ||
| A standard for CSV files is provided in RFC 4180, but since the | ||
| format predates that standard by decades, there are many minor | ||
| differences in CSV file consumers and their expectations. The CSV | ||
| encoder has a number of options to tailor output to those | ||
| expectations. | ||
| .Pp | ||
| Consider the following XML: | ||
| .Bd -literal -offset indent | ||
| % list-items --libxo xml,pretty | ||
| <top> | ||
| <data test="value"> | ||
| <item test2="value2"> | ||
| <sku test3="value3" key="key">GRO-000-415</sku> | ||
| <name key="key">gum</name> | ||
| <sold>1412</sold> | ||
| <in-stock>54</in-stock> | ||
| <on-order>10</on-order> | ||
| </item> | ||
| <item> | ||
| <sku test3="value3" key="key">HRD-000-212</sku> | ||
| <name key="key">rope</name> | ||
| <sold>85</sold> | ||
| <in-stock>4</in-stock> | ||
| <on-order>2</on-order> | ||
| </item> | ||
| <item> | ||
| <sku test3="value3" key="key">HRD-000-517</sku> | ||
| <name key="key">ladder</name> | ||
| <sold>0</sold> | ||
| <in-stock>2</in-stock> | ||
| <on-order>1</on-order> | ||
| </item> | ||
| </data> | ||
| </top> | ||
| .Ed | ||
| .Pp | ||
| This output is a list of `instances` (named "item"), each containing a | ||
| set of `leafs` ("sku", "name", etc). | ||
| .Pp | ||
| The CSV encoder will emit the leaf values in this output as `fields` | ||
| inside a CSV `record`, which is a line containing a set of | ||
| comma-separated values: | ||
| .Bd -literal -offset indent | ||
| % list-items --libxo encoder=csv | ||
| sku,name,sold,in-stock,on-order | ||
| GRO-000-415,gum,1412,54,10 | ||
| HRD-000-212,rope,85,4,2 | ||
| HRD-000-517,ladder,0,2,1 | ||
| .Ed | ||
| .Pp | ||
| Be aware that since the CSV encoder looks for data instances, when | ||
| used with | ||
| .Nm xo , | ||
| the `--instance` option will be needed: | ||
| .Bd -literal -offset indent | ||
| % xo --libxo encoder=csv --instance foo 'The {:product} is {:status}\n' stereo "in route" | ||
| product,status | ||
| stereo,in route | ||
| .Ed | ||
| .Sh The "path" Option | ||
| By default, the CSV encoder will attempt to emit any list instance | ||
| generated by the application. | ||
| In some cases, this may be unacceptable, and a specific list may be | ||
| desired. | ||
| .Pp | ||
| Use the "path" option to limit the processing of output to a specific | ||
| hierarchy. The path should be one or more names of containers or | ||
| lists. | ||
| .Pp | ||
| For example, if the "list-items" application generates other lists, | ||
| the user can give "path=top/data/item" as a path: | ||
| .Bd -literal -offset indent | ||
| % list-items --libxo encoder=csv:path=top/data/item | ||
| sku,name,sold,in-stock,on-order | ||
| GRO-000-415,gum,1412,54,10 | ||
| HRD-000-212,rope,85,4,2 | ||
| HRD-000-517,ladder,0,2,1 | ||
| .Ed | ||
| .Pp | ||
| Paths are "relative", meaning they need not be a complete set | ||
| of names to the list. This means that "path=item" may be sufficient | ||
| for the above example. | ||
| .Sh The "leafs" Option | ||
| The CSV encoding requires that all lines of output have the same | ||
| number of fields with the same order. In contrast, XML and JSON allow | ||
| any order (though libxo forces key leafs to appear before other | ||
| leafs). | ||
| .Pp | ||
| To maintain a consistent set of fields inside the CSV file, the same | ||
| set of leafs must be selected from each list item. By default, the | ||
| CSV encoder records the set of leafs that appear in the first list | ||
| instance it processes, and extract only those leafs from future | ||
| instances. If the first instance is missing a leaf that is desired by | ||
| the consumer, the "leaf" option can be used to ensure that an empty | ||
| value is recorded for instances that lack a particular leaf. | ||
| .Pp | ||
| The "leafs" option can also be used to exclude leafs, limiting the | ||
| output to only those leafs provided. | ||
| .Pp | ||
| In addition, the order of the output fields follows the order in which | ||
| the leafs are listed. "leafs=one.two" and "leafs=two.one" give | ||
| distinct output. | ||
| .Pp | ||
| So the "leafs" option can be used to expand, limit, and order the set | ||
| of leafs. | ||
| .Pp | ||
| The value of the leafs option should be one or more leaf names, | ||
| separated by a period ("."): | ||
| .Bd -literal -offset indent | ||
| % list-items --libxo encoder=csv:leafs=sku.on-order | ||
| sku,on-order | ||
| GRO-000-415,10 | ||
| HRD-000-212,2 | ||
| HRD-000-517,1 | ||
| % list-items -libxo encoder=csv:leafs=on-order.sku | ||
| on-order,sku | ||
| 10,GRO-000-415 | ||
| 2,HRD-000-212 | ||
| 1,HRD-000-517 | ||
| .Ed | ||
| .Pp | ||
| Note that since libxo uses terminology from YANG (:RFC:`7950`), the | ||
| data modeling language for NETCONF (:RFC:`6241`), which uses "leafs" | ||
| as the plural form of "leaf". libxo follows that convention. | ||
| .Sh The "no-header" Option | ||
| CSV files typical begin with a line that defines the fields included | ||
| in that file, in an attempt to make the contents self-defining: | ||
| .Bd -literal -offset indent | ||
| sku,name,sold,in-stock,on-order | ||
| GRO-000-415,gum,1412,54,10 | ||
| HRD-000-212,rope,85,4,2 | ||
| HRD-000-517,ladder,0,2,1 | ||
| .Ed | ||
| .Pp | ||
| There is no reliable mechanism for determining whether this header | ||
| line is included, so the consumer must make an assumption. | ||
| .Pp | ||
| The csv encoder defaults to producing the header line, but the | ||
| "no-header" option can be included to avoid the header line. | ||
| .Sh The "no-quotes" Option | ||
| RFC 4180 specifies that fields containing spaces should be quoted, but | ||
| many CSV consumers do not handle quotes. The "no-quotes" option | ||
| instruct the CSV encoder to avoid the use of quotes. | ||
| .Sh The "dos" Option | ||
| RFC 4180 defines the end-of-line marker as a carriage return | ||
| followed by a newline. This "CRLF" convention dates from the distant | ||
| past, but its use was anchored in the 1980s by the `DOS` operating | ||
| system. | ||
| .Pp | ||
| The CSV encoder defaults to using the standard Unix end-of-line | ||
| marker, a simple newline. Use the "dos" option to use the `CRLF` | ||
| convention. | ||
| .Sh Option Handling | ||
| The handling of command-line options is complex, since there are three | ||
| hierarchies in use, but the rules are: | ||
| .Bl -bullet | ||
| .It | ||
| commas separate | ||
| .Nm libxo | ||
| options | ||
| .Bd -literal -ofset indent | ||
| \-\-libxo json,pretty,warn | ||
| .Ed | ||
| .It | ||
| pluses separate encoder options | ||
| .Bd -literal -ofset indent | ||
| \-\-libxo @csv+dos+no-header,warn | ||
| .Ed | ||
| .It | ||
| periods separate tag names | ||
| .Bd -literal -ofset indent | ||
| \-\-libxo @csv+leafs=name.used.free+dos,warn | ||
| .El | ||
| .Sh SEE ALSO | ||
| .Xr libxo 3 , | ||
| .Xr xo_options 7 | ||
| .Sh HISTORY | ||
| The | ||
| .Nm libxo | ||
| library first appeared in | ||
| .Fx 11.0 . | ||
| The CSV encoder first appeared in | ||
| .Fx 13.0 . | ||
| .Sh AUTHORS | ||
| .Nm libxo | ||
| was written by | ||
| .An Phil Shafer Aq Mt phil@freebsd.org . | ||
|
|
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