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# Importing and exporting custom text data using templates and regex in ClickHouse

> Page describing how to import and export custom text using templates and regex in ClickHouse

We often have to deal with data in custom text formats. That could be a non-standard format, invalid JSON, or a broken CSV. Using standard parsers like CSV or JSON won't work in all such cases. But ClickHouse has us covered here with powerful Template and Regex formats.

<h2 id="importing-based-on-a-template">
  Importing based on a template
</h2>

Suppose we want to import data from the following [log file](https://clickhouse-docs-assets.s3.us-east-1.amazonaws.com/error.log):

```bash theme={null}
head error.log
```

```response theme={null}
2023/01/15 14:51:17 [error]  client: 7.2.8.1, server: example.com "GET /apple-touch-icon-120x120.png HTTP/1.1"
2023/01/16 06:02:09 [error]  client: 8.4.2.7, server: example.com "GET /apple-touch-icon-120x120.png HTTP/1.1"
2023/01/15 13:46:13 [error]  client: 6.9.3.7, server: example.com "GET /apple-touch-icon.png HTTP/1.1"
2023/01/16 05:34:55 [error]  client: 9.9.7.6, server: example.com "GET /h5/static/cert/icon_yanzhengma.png HTTP/1.1"
```

We can use a [Template](/reference/formats/Template/Template) format to import this data. We have to define a template string with values placeholders for each row of input data:

```response theme={null}
<time> [error] client: <ip>, server: <host> "<request>"
```

Let's create a table to import our data into:

```sql theme={null}
CREATE TABLE error_log
(
    `time` DateTime,
    `ip` String,
    `host` String,
    `request` String
)
ENGINE = MergeTree
ORDER BY (host, request, time)
```

To import data using a given template, we have to save our template string in a file ([row.template](https://clickhouse-docs-assets.s3.us-east-1.amazonaws.com/row.template) in our case):

```response theme={null}
${time:Escaped} [error]  client: ${ip:CSV}, server: ${host:CSV} ${request:JSON}
```

We define a name of a column and escaping rule in a `${name:escaping}` format. Multiple options are available here, like CSV, JSON, Escaped, or Quoted, which implement [respective escaping rules](/reference/formats/Template/Template).

Now we can use the given file as an argument to the `format_template_row` settings option while importing data (*note, that template and data files **shouldn't have** an extra `\n` symbol at the end of file*):

```sql theme={null}
INSERT INTO error_log FROM INFILE 'error.log'
SETTINGS format_template_row = 'row.template'
FORMAT Template
```

And we can make sure our data was loaded into the table:

```sql theme={null}
SELECT
    request,
    count(*)
FROM error_log
GROUP BY request
```

```response theme={null}
┌─request──────────────────────────────────────────┬─count()─┐
│ GET /img/close.png HTTP/1.1                      │     176 │
│ GET /h5/static/cert/icon_yanzhengma.png HTTP/1.1 │     172 │
│ GET /phone/images/icon_01.png HTTP/1.1           │     139 │
│ GET /apple-touch-icon-precomposed.png HTTP/1.1   │     161 │
│ GET /apple-touch-icon.png HTTP/1.1               │     162 │
│ GET /apple-touch-icon-120x120.png HTTP/1.1       │     190 │
└──────────────────────────────────────────────────┴─────────┘
```

<h3 id="skipping-whitespaces">
  Skipping whitespaces
</h3>

Consider using [TemplateIgnoreSpaces](/reference/formats/Template/TemplateIgnoreSpaces), which allows skipping whitespaces between delimiters in a template:

```text theme={null}
Template:               -->  "p1: ${p1:CSV}, p2: ${p2:CSV}"
TemplateIgnoreSpaces    -->  "p1:${p1:CSV}, p2:${p2:CSV}"
```

<h2 id="exporting-data-using-templates">
  Exporting data using templates
</h2>

We can also export data to any text format using templates as well. In this case, we have to create two files:

[Result set template](https://clickhouse-docs-assets.s3.us-east-1.amazonaws.com/output.results), which defines the layout for the whole result set:

```response theme={null}
== Top 10 IPs ==
${data}
--- ${rows_read:XML} rows read in ${time:XML} ---
```

Here, `rows_read` and `time` are system metrics available for each request. While `data` stands for generated rows (`${data}` should always come as a first placeholder in this file), based on a template defined in a [**row template file**](https://clickhouse-docs-assets.s3.us-east-1.amazonaws.com/output.rows):

```response theme={null}
${ip:Escaped} generated ${total:Escaped} requests
```

Now let's use these templates to export the following query:

```sql theme={null}
SELECT
    ip,
    count() AS total
FROM error_log GROUP BY ip ORDER BY total DESC LIMIT 10
FORMAT Template SETTINGS format_template_resultset = 'output.results',
                         format_template_row = 'output.rows';

== Top 10 IPs ==

9.8.4.6 generated 3 requests
9.5.1.1 generated 3 requests
2.4.8.9 generated 3 requests
4.8.8.2 generated 3 requests
4.5.4.4 generated 3 requests
3.3.6.4 generated 2 requests
8.9.5.9 generated 2 requests
2.5.1.8 generated 2 requests
6.8.3.6 generated 2 requests
6.6.3.5 generated 2 requests

--- 1000 rows read in 0.001380604 ---
```

<h3 id="exporting-to-html-files">
  Exporting to HTML files
</h3>

Template-based results can also be exported to files using an [`INTO OUTFILE`](/reference/statements/select/into-outfile) clause. Let's generate HTML files based on given [resultset](https://clickhouse-docs-assets.s3.us-east-1.amazonaws.com/html.results) and [row](https://clickhouse-docs-assets.s3.us-east-1.amazonaws.com/html.row) formats:

```sql theme={null}
SELECT
    ip,
    count() AS total
FROM error_log GROUP BY ip ORDER BY total DESC LIMIT 10
INTO OUTFILE 'out.html'
FORMAT Template
SETTINGS format_template_resultset = 'html.results',
         format_template_row = 'html.row'
```

<h3 id="exporting-to-xml">
  Exporting to XML
</h3>

Template format can be used to generate all imaginable text format files, including XML. Just put a relevant template and do the export.

Also consider using an [XML](/reference/formats/XML) format to get standard XML results including metadata:

```sql theme={null}
SELECT *
FROM error_log
LIMIT 3
FORMAT XML
```

```xml theme={null}
<?xml version='1.0' encoding='UTF-8' ?>
<result>
        <meta>
                <columns>
                        <column>
                                <name>time</name>
                                <type>DateTime</type>
                        </column>
                        ...
                </columns>
        </meta>
        <data>
                <row>
                        <time>2023-01-15 13:00:01</time>
                        <ip>3.5.9.2</ip>
                        <host>example.com</host>
                        <request>GET /apple-touch-icon-120x120.png HTTP/1.1</request>
                </row>
                ...
        </data>
        <rows>3</rows>
        <rows_before_limit_at_least>1000</rows_before_limit_at_least>
        <statistics>
                <elapsed>0.000745001</elapsed>
                <rows_read>1000</rows_read>
                <bytes_read>88184</bytes_read>
        </statistics>
</result>

```

<h2 id="importing-data-based-on-regular-expressions">
  Importing data based on regular expressions
</h2>

[Regexp](/reference/formats/Regexp) format addresses more sophisticated cases when input data needs to be parsed in a more complex way. Let's parse our [error.log](https://clickhouse-docs-assets.s3.us-east-1.amazonaws.com/error.log) example file, but capture the file name and protocol this time to save them into separate columns. First, let's prepare a new table for that:

```sql theme={null}
CREATE TABLE error_log
(
    `time` DateTime,
    `ip` String,
    `host` String,
    `file` String,
    `protocol` String
)
ENGINE = MergeTree
ORDER BY (host, file, time)
```

Now we can import data based on a regular expression:

```sql theme={null}
INSERT INTO error_log FROM INFILE 'error.log'
SETTINGS
  format_regexp = '(.+?) \\[error\\]  client: (.+), server: (.+?) "GET .+?([^/]+\\.[^ ]+) (.+?)"'
FORMAT Regexp
```

ClickHouse will insert data from each capture group into the relevant column based on its order. Let's check the data:

```sql theme={null}
SELECT * FROM error_log LIMIT 5
```

```response theme={null}
┌────────────────time─┬─ip──────┬─host────────┬─file─────────────────────────┬─protocol─┐
│ 2023-01-15 13:00:01 │ 3.5.9.2 │ example.com │ apple-touch-icon-120x120.png │ HTTP/1.1 │
│ 2023-01-15 13:01:40 │ 3.7.2.5 │ example.com │ apple-touch-icon-120x120.png │ HTTP/1.1 │
│ 2023-01-15 13:16:49 │ 9.2.9.2 │ example.com │ apple-touch-icon-120x120.png │ HTTP/1.1 │
│ 2023-01-15 13:21:38 │ 8.8.5.3 │ example.com │ apple-touch-icon-120x120.png │ HTTP/1.1 │
│ 2023-01-15 13:31:27 │ 9.5.8.4 │ example.com │ apple-touch-icon-120x120.png │ HTTP/1.1 │
└─────────────────────┴─────────┴─────────────┴──────────────────────────────┴──────────┘
```

By default, ClickHouse will raise an error in case of unmatched rows. If you want to skip unmatched rows instead, enable it using [format\_regexp\_skip\_unmatched](/reference/settings/formats#format_regexp_skip_unmatched) option:

```sql theme={null}
SET format_regexp_skip_unmatched = 1;
```

<h2 id="other-formats">
  Other formats
</h2>

ClickHouse introduces support for many formats, both text, and binary, to cover various scenarios and platforms. Explore more formats and ways to work with them in the following articles:

* [CSV and TSV formats](/guides/clickhouse/data-formats/csv-tsv)
* [Parquet](/guides/clickhouse/data-formats/parquet)
* [JSON formats](/guides/clickhouse/data-formats/json/intro)
* **Regex and templates**
* [Native and binary formats](/guides/clickhouse/data-formats/binary)
* [SQL formats](/guides/clickhouse/data-formats/sql)

And also check [clickhouse-local](https://clickhouse.com/blog/extracting-converting-querying-local-files-with-sql-clickhouse-local) - a portable full-featured tool to work on local/remote files without the need for Clickhouse server.