Add DCF (Debian Control Format) as supported file type (#1970)

* reader

* record writer

* pkg/output/record_writer_dcf.go

* test/input/test.dcf

* test/cases/io-dcf/

* pkg/cli/option_parse.go

* make fmt

* make dev

* docs and `make dev`

docs/src/data/sample.dcf

@@ -0,0 +1,9 @@
+Package: foo
+Version: 1.0
+Depends: libc6 (>= 2.0), libfoo (>= 1.2)
+Description: A test package.
+
+Package: bar
+Version: 2.0
+Recommends: foo
+Description: Another package.

docs/src/features.md

@@ -17,7 +17,7 @@ Quick links:
 # Features
 
 Miller is like awk, sed, cut, join, and sort for **name-indexed data, such as
-CSV, TSV, JSON, JSON Lines, and YAML**. You get to work with your data using named
+CSV, TSV, JSON, JSON Lines, YAML, and DCF**. You get to work with your data using named
 fields, without needing to count positional column indices.
 
 This is something the Unix toolkit always could have done, and arguably always
@@ -25,7 +25,7 @@ should have done.  It operates on key-value-pair data while the familiar Unix
 tools operate on integer-indexed fields: if the natural data structure for the
 latter is the array, then Miller's natural data structure is the
 insertion-ordered hash map.  This encompasses a **variety of data formats**,
-including but not limited to the familiar CSV, TSV, JSON, JSON Lines, and YAML.
+including but not limited to the familiar CSV, TSV, JSON, JSON Lines, YAML, and DCF.
 (Miller can handle **positionally-indexed data** as a special case.)
 
 * Miller is **multi-purpose**: it's useful for **data cleaning**, **data reduction**, **statistical reporting**, **devops**, **system administration**, **log-file processing**, **format conversion**, and **database-query post-processing**.

docs/src/features.md.in

@@ -1,7 +1,7 @@
 # Features
 
 Miller is like awk, sed, cut, join, and sort for **name-indexed data, such as
-CSV, TSV, JSON, JSON Lines, and YAML**. You get to work with your data using named
+CSV, TSV, JSON, JSON Lines, YAML, and DCF**. You get to work with your data using named
 fields, without needing to count positional column indices.
 
 This is something the Unix toolkit always could have done, and arguably always
@@ -9,7 +9,7 @@ should have done.  It operates on key-value-pair data while the familiar Unix
 tools operate on integer-indexed fields: if the natural data structure for the
 latter is the array, then Miller's natural data structure is the
 insertion-ordered hash map.  This encompasses a **variety of data formats**,
-including but not limited to the familiar CSV, TSV, JSON, JSON Lines, and YAML.
+including but not limited to the familiar CSV, TSV, JSON, JSON Lines, YAML, and DCF.
 (Miller can handle **positionally-indexed data** as a special case.)
 
 * Miller is **multi-purpose**: it's useful for **data cleaning**, **data reduction**, **statistical reporting**, **devops**, **system administration**, **log-file processing**, **format conversion**, and **database-query post-processing**.

docs/src/file-formats.md

@@ -17,7 +17,7 @@ Quick links:
 # File formats
 
 Miller handles name-indexed data using several formats: some you probably know
-by name, such as CSV, TSV, JSON, JSON Lines, and YAML -- and other formats you're likely already
+by name, such as CSV, TSV, JSON, JSON Lines, YAML, and DCF -- and other formats you're likely already
 seeing and using in your structured data.
 
 Additionally, Miller gives you the option to include comments within your data.
@@ -108,6 +108,17 @@ NIDX: implicitly numerically indexed (Unix-toolkit style)
 | the quick brown     | Record 1: "1":"the", "2":"quick", "3":"brown"
 | fox jumped          | Record 2: "1":"fox", "2":"jumped"
 +---------------------+
+
+DCF: Debian control file format
++------------+
+| apple: 1   |
+| bat: 2     |
+| cog: 3     |
+|            |
+| dish: 7    |
+| egg: 8     |
+| 3: flint   |
++------------+
 </pre>
 
 ## CSV/TSV/ASV/USV/etc.
@@ -720,6 +731,43 @@ the dawn's
 light
 </pre>
 
+## DCF (Debian control file)
+
+<pre class="pre-highlight-in-pair">
+<b>cat data/sample.dcf</b>
+</pre>
+<pre class="pre-non-highlight-in-pair">
+Package: foo
+Version: 1.0
+Depends: libc6 (>= 2.0), libfoo (>= 1.2)
+Description: A test package.
+
+Package: bar
+Version: 2.0
+Recommends: foo
+Description: Another package.
+</pre>
+
+<pre class="pre-highlight-in-pair">
+<b>mlr -i dcf -o json cat data/sample.dcf</b>
+</pre>
+<pre class="pre-non-highlight-in-pair">
+[
+{
+  "Package": "foo",
+  "Version": "1.0",
+  "Depends": ["libc6 (>= 2.0)", "libfoo (>= 1.2)"],
+  "Description": "A test package."
+},
+{
+  "Package": "bar",
+  "Version": "2.0",
+  "Recommends": ["foo"],
+  "Description": "Another package."
+}
+]
+</pre>
+
 ## Data-conversion keystroke-savers
 
 While you can do format conversion using `mlr --icsv --ojson cat myfile.csv`, there are also keystroke-savers for this purpose, such as `mlr --c2j cat myfile.csv`.  For a complete list:
@@ -731,7 +779,7 @@ While you can do format conversion using `mlr --icsv --ojson cat myfile.csv`, th
 FORMAT-CONVERSION KEYSTROKE-SAVER FLAGS
 As keystroke-savers for format-conversion you may use the following.
 The letters c, t, j, l, d, n, x, p, m, and y refer to formats CSV, TSV, JSON, JSON Lines,
-DKVP, NIDX, XTAB, PPRINT, markdown, and YAML, respectively.
+DKVP, NIDX, XTAB, PPRINT, markdown, and YAML, respectively. DCF is also supported (use --dcf for DCF in and out).
 
 | In\out   | CSV      | TSV      | JSON     | JSONL | DKVP  | NIDX  | XTAB  | PPRINT | Markdown | YAML   |
 +----------+----------+----------+----------+-------+-------+-------+-------+--------+----------+--------+

docs/src/file-formats.md.in

@@ -1,7 +1,7 @@
 # File formats
 
 Miller handles name-indexed data using several formats: some you probably know
-by name, such as CSV, TSV, JSON, JSON Lines, and YAML -- and other formats you're likely already
+by name, such as CSV, TSV, JSON, JSON Lines, YAML, and DCF -- and other formats you're likely already
 seeing and using in your structured data.
 
 Additionally, Miller gives you the option to include comments within your data.
@@ -362,6 +362,16 @@ GENMD-RUN-COMMAND
 mlr --nidx --fs ' ' --repifs cut -f 2,3 data/mydata.txt
 GENMD-EOF
 
+## DCF (Debian control file)
+
+GENMD-RUN-COMMAND
+cat data/sample.dcf
+GENMD-EOF
+
+GENMD-RUN-COMMAND
+mlr -i dcf -o json cat data/sample.dcf
+GENMD-EOF
+
 ## Data-conversion keystroke-savers
 
 While you can do format conversion using `mlr --icsv --ojson cat myfile.csv`, there are also keystroke-savers for this purpose, such as `mlr --c2j cat myfile.csv`.  For a complete list:

docs/src/glossary.md

@@ -468,7 +468,7 @@ trying to define a [local variable](#local-variable) `if = 3` will result in a p
 A subsequence of a text file in between line-ending symbols such as the special linefeed character.
 Tools in the [Unix toolkit](#unix-toolkit) generally operate on lines; Miller is designed to do
 that (using the [NIDX format flags](file-formats.md#nidx-index-numbered-toolkit-style)), as well
-as non-line-oriented formats such as [CSV, TSV, JSON, YAML, and others](file-formats.md).
+as non-line-oriented formats such as [CSV, TSV, JSON, YAML, DCF, and others](file-formats.md).
 
 ## local variable
 

docs/src/glossary.md.in

@@ -452,7 +452,7 @@ trying to define a [local variable](#local-variable) `if = 3` will result in a p
 A subsequence of a text file in between line-ending symbols such as the special linefeed character.
 Tools in the [Unix toolkit](#unix-toolkit) generally operate on lines; Miller is designed to do
 that (using the [NIDX format flags](file-formats.md#nidx-index-numbered-toolkit-style)), as well
-as non-line-oriented formats such as [CSV, TSV, JSON, YAML, and others](file-formats.md).
+as non-line-oriented formats such as [CSV, TSV, JSON, YAML, DCF, and others](file-formats.md).
 
 ## local variable
 

docs/src/index.md

@@ -16,7 +16,7 @@ Quick links:
 </div>
 # Introduction
 
-**Miller is a command-line tool for querying, shaping, and reformatting data files in various formats, including CSV, TSV, JSON, JSON Lines, and YAML.**
+**Miller is a command-line tool for querying, shaping, and reformatting data files in various formats, including CSV, TSV, JSON, JSON Lines, YAML, and DCF.**
 
 **The big picture:** Even well into the 21st century, our world is full of text-formatted data such as CSV. Google _CSV memes_, for example. We need tooling to _thrive in this world_, nimbly manipulating data which is in CSVs. And we need tooling to _move beyond CSV_, to be able to pull data out and into other storage and processing systems. Miller is designed for both of these goals.
 
@@ -39,7 +39,7 @@ pretty-print your data horizontally or vertically to make it easier to read.
 <b>mlr --json head -n 1 myfile.json</b>
 </pre>
 
-The `sort`, `head`, etc., are called *verbs*. They're analogs of familiar command-line tools like `sort`, `head`, and so on -- but they're aware of name-indexed, multi-line file formats like CSV, TSV, JSON, and YAML. In addition, though, using Miller's `put` verb, you can use programming-language statements for expressions like
+The `sort`, `head`, etc., are called *verbs*. They're analogs of familiar command-line tools like `sort`, `head`, and so on -- but they're aware of name-indexed, multi-line file formats like CSV, TSV, JSON, YAML, and DCF. In addition, though, using Miller's `put` verb, you can use programming-language statements for expressions like
 
 <pre class="pre-highlight-non-pair">
 <b>mlr --csv put '$rate = $units / $seconds' input.csv</b>

docs/src/index.md.in

@@ -1,6 +1,6 @@
 # Introduction
 
-**Miller is a command-line tool for querying, shaping, and reformatting data files in various formats, including CSV, TSV, JSON, JSON Lines, and YAML.**
+**Miller is a command-line tool for querying, shaping, and reformatting data files in various formats, including CSV, TSV, JSON, JSON Lines, YAML, and DCF.**
 
 **The big picture:** Even well into the 21st century, our world is full of text-formatted data such as CSV. Google _CSV memes_, for example. We need tooling to _thrive in this world_, nimbly manipulating data which is in CSVs. And we need tooling to _move beyond CSV_, to be able to pull data out and into other storage and processing systems. Miller is designed for both of these goals.
 
@@ -23,7 +23,7 @@ GENMD-SHOW-COMMAND
 mlr --json head -n 1 myfile.json
 GENMD-EOF
 
-The `sort`, `head`, etc., are called *verbs*. They're analogs of familiar command-line tools like `sort`, `head`, and so on -- but they're aware of name-indexed, multi-line file formats like CSV, TSV, JSON, and YAML. In addition, though, using Miller's `put` verb, you can use programming-language statements for expressions like
+The `sort`, `head`, etc., are called *verbs*. They're analogs of familiar command-line tools like `sort`, `head`, and so on -- but they're aware of name-indexed, multi-line file formats like CSV, TSV, JSON, YAML, and DCF. In addition, though, using Miller's `put` verb, you can use programming-language statements for expressions like
 
 GENMD-SHOW-COMMAND
 mlr --csv put '$rate = $units / $seconds' input.csv

docs/src/manpage.md

@@ -141,6 +141,17 @@ This is simply a copy of what you should see on running `man mlr` at a command p
        | fox jumped          | Record 2: "1":"fox", "2":"jumped"
        +---------------------+
 
+       DCF: Debian control file format
+       +------------+
+       | apple: 1   |
+       | bat: 2     |
+       | cog: 3     |
+       |            |
+       | dish: 7    |
+       | egg: 8     |
+       | 3: flint   |
+       +------------+
+
 1mHELP OPTIONS0m
        Type 'mlr help {topic}' for any of the following:
        Essentials:
@@ -393,6 +404,8 @@ This is simply a copy of what you should see on running `man mlr` at a command p
        --asv or --asvlite       Use ASV format for input and output data.
        --csv or -c or --c2c     Use CSV format for input and output data.
        --csvlite                Use CSV-lite format for input and output data.
+       --dcf                    Use Debian control file (DCF) format for input and
+                                output data.
        --dkvp or --d2d          Use DKVP format for input and output data.
        --gen-field-name         Specify field name for --igen. Defaults to "i".
        --gen-start              Specify start value for --igen. Defaults to 1.
@@ -401,6 +414,7 @@ This is simply a copy of what you should see on running `man mlr` at a command p
        --iasv or --iasvlite     Use ASV format for input data.
        --icsv                   Use CSV format for input data.
        --icsvlite               Use CSV-lite format for input data.
+       --idcf                   Use Debian control file (DCF) format for input data.
        --idkvp                  Use DKVP format for input data.
        --igen                   Ignore input files and instead generate sequential
                                 numeric input using --gen-field-name, --gen-start,
@@ -424,6 +438,7 @@ This is simply a copy of what you should see on running `man mlr` at a command p
        --oasv or --oasvlite     Use ASV format for output data.
        --ocsv                   Use CSV format for output data.
        --ocsvlite               Use CSV-lite format for output data.
+       --odcf                   Use Debian control file (DCF) format for output data.
        --odkvp                  Use DKVP format for output data.
        --ojson                  Use JSON format for output data.
        --ojsonl                 Use JSON Lines format for output data.
@@ -470,7 +485,7 @@ This is simply a copy of what you should see on running `man mlr` at a command p
 1mFORMAT-CONVERSION KEYSTROKE-SAVER FLAGS0m
        As keystroke-savers for format-conversion you may use the following.
        The letters c, t, j, l, d, n, x, p, m, and y refer to formats CSV, TSV, JSON, JSON Lines,
-       DKVP, NIDX, XTAB, PPRINT, markdown, and YAML, respectively.
+       DKVP, NIDX, XTAB, PPRINT, markdown, and YAML, respectively. DCF is also supported (use --dcf for DCF in and out).
 
        | In\out   | CSV      | TSV      | JSON     | JSONL | DKVP  | NIDX  | XTAB  | PPRINT | Markdown | YAML   |
        +----------+----------+----------+----------+-------+-------+-------+-------+--------+----------+--------+
@@ -837,6 +852,7 @@ This is simply a copy of what you should see on running `man mlr` at a command p
                Format   FS     PS     RS
                csv      ","    N/A    "\n"
                csvlite  ","    N/A    "\n"
+               dcf      N/A    N/A    N/A
                dkvp     ","    "="    "\n"
                gen      ","    N/A    "\n"
                json     N/A    N/A    N/A
@@ -3787,5 +3803,5 @@ This is simply a copy of what you should see on running `man mlr` at a command p
        MIME Type for Comma-Separated Values (CSV) Files, the Miller docsite
        https://miller.readthedocs.io
 
-                                  2026-02-15                         4mMILLER24m(1)
+                                  2026-02-16                         4mMILLER24m(1)
 </pre>

docs/src/manpage.txt

@@ -120,6 +120,17 @@
        | fox jumped          | Record 2: "1":"fox", "2":"jumped"
        +---------------------+
 
+       DCF: Debian control file format
+       +------------+
+       | apple: 1   |
+       | bat: 2     |
+       | cog: 3     |
+       |            |
+       | dish: 7    |
+       | egg: 8     |
+       | 3: flint   |
+       +------------+
+
 1mHELP OPTIONS0m
        Type 'mlr help {topic}' for any of the following:
        Essentials:
@@ -372,6 +383,8 @@
        --asv or --asvlite       Use ASV format for input and output data.
        --csv or -c or --c2c     Use CSV format for input and output data.
        --csvlite                Use CSV-lite format for input and output data.
+       --dcf                    Use Debian control file (DCF) format for input and
+                                output data.
        --dkvp or --d2d          Use DKVP format for input and output data.
        --gen-field-name         Specify field name for --igen. Defaults to "i".
        --gen-start              Specify start value for --igen. Defaults to 1.
@@ -380,6 +393,7 @@
        --iasv or --iasvlite     Use ASV format for input data.
        --icsv                   Use CSV format for input data.
        --icsvlite               Use CSV-lite format for input data.
+       --idcf                   Use Debian control file (DCF) format for input data.
        --idkvp                  Use DKVP format for input data.
        --igen                   Ignore input files and instead generate sequential
                                 numeric input using --gen-field-name, --gen-start,
@@ -403,6 +417,7 @@
        --oasv or --oasvlite     Use ASV format for output data.
        --ocsv                   Use CSV format for output data.
        --ocsvlite               Use CSV-lite format for output data.
+       --odcf                   Use Debian control file (DCF) format for output data.
        --odkvp                  Use DKVP format for output data.
        --ojson                  Use JSON format for output data.
        --ojsonl                 Use JSON Lines format for output data.
@@ -449,7 +464,7 @@
 1mFORMAT-CONVERSION KEYSTROKE-SAVER FLAGS0m
        As keystroke-savers for format-conversion you may use the following.
        The letters c, t, j, l, d, n, x, p, m, and y refer to formats CSV, TSV, JSON, JSON Lines,
-       DKVP, NIDX, XTAB, PPRINT, markdown, and YAML, respectively.
+       DKVP, NIDX, XTAB, PPRINT, markdown, and YAML, respectively. DCF is also supported (use --dcf for DCF in and out).
 
        | In\out   | CSV      | TSV      | JSON     | JSONL | DKVP  | NIDX  | XTAB  | PPRINT | Markdown | YAML   |
        +----------+----------+----------+----------+-------+-------+-------+-------+--------+----------+--------+
@@ -816,6 +831,7 @@
                Format   FS     PS     RS
                csv      ","    N/A    "\n"
                csvlite  ","    N/A    "\n"
+               dcf      N/A    N/A    N/A
                dkvp     ","    "="    "\n"
                gen      ","    N/A    "\n"
                json     N/A    N/A    N/A
@@ -3766,4 +3782,4 @@
        MIME Type for Comma-Separated Values (CSV) Files, the Miller docsite
        https://miller.readthedocs.io
 
-                                  2026-02-15                         4mMILLER24m(1)
+                                  2026-02-16                         4mMILLER24m(1)

docs/src/mk-flag-info.rb

@@ -16,7 +16,7 @@ for section_name in section_names
     # The markdown in this section looks a lot better when hand-crafted (thanks Nikos!).
     puts <<EOF
 The letters `c`, `t`, `j`, `l`, `d`, `n`, `x`, `p`, `m`, and `y` refer to formats CSV, TSV, JSON, JSON Lines,
-DKVP, NIDX, XTAB, PPRINT, markdown, and YAML, respectively. Note that markdown format is available for
+DKVP, NIDX, XTAB, PPRINT, markdown, and YAML, respectively. DCF is also supported (use `--dcf` for DCF in and out). Note that markdown format is available for
 output only.
 
 | In \\ out  | **CSV** | **TSV** | **JSON** | **JSONL** | **DKVP** | **NIDX** | **XTAB** | **PPRINT** | **Markdown** | **YAML** |

docs/src/reference-main-data-types.md

@@ -47,7 +47,7 @@ See also [Differences from other programming languages](reference-dsl-difference
 
 Miller's input and output are all text-oriented: all the
 [file formats supported by Miller](file-formats.md) are human-readable text,
-such as CSV, TSV, and JSON; binary formats such as
+such as CSV, TSV, JSON, and DCF; binary formats such as
 [BSON](https://bsonspec.org/) and [Parquet](https://parquet.apache.org/) are
 not supported (as of mid-2021). In this sense, everything is a string in and out of
 Miller -- be it in data files, or in DSL expressions you key in.

docs/src/reference-main-data-types.md.in

@@ -31,7 +31,7 @@ See also [Differences from other programming languages](reference-dsl-difference
 
 Miller's input and output are all text-oriented: all the
 [file formats supported by Miller](file-formats.md) are human-readable text,
-such as CSV, TSV, and JSON; binary formats such as
+such as CSV, TSV, JSON, and DCF; binary formats such as
 [BSON](https://bsonspec.org/) and [Parquet](https://parquet.apache.org/) are
 not supported (as of mid-2021). In this sense, everything is a string in and out of
 Miller -- be it in data files, or in DSL expressions you key in.

docs/src/reference-main-flag-list.md

@@ -155,6 +155,7 @@ are overridden in all cases by setting output format to `format2`.
 * `--asv or --asvlite`: Use ASV format for input and output data.
 * `--csv or -c or --c2c`: Use CSV format for input and output data.
 * `--csvlite`: Use CSV-lite format for input and output data.
+* `--dcf`: Use Debian control file (DCF) format for input and output data.
 * `--dkvp or --d2d`: Use DKVP format for input and output data.
 * `--gen-field-name`: Specify field name for --igen. Defaults to "i".
 * `--gen-start`: Specify start value for --igen. Defaults to 1.
@@ -163,6 +164,7 @@ are overridden in all cases by setting output format to `format2`.
 * `--iasv or --iasvlite`: Use ASV format for input data.
 * `--icsv`: Use CSV format for input data.
 * `--icsvlite`: Use CSV-lite format for input data.
+* `--idcf`: Use Debian control file (DCF) format for input data.
 * `--idkvp`: Use DKVP format for input data.
 * `--igen`: Ignore input files and instead generate sequential numeric input using --gen-field-name, --gen-start, --gen-step, and --gen-stop values. See also the seqgen verb, which is more useful/intuitive.
 * `--ijson`: Use JSON format for input data.
@@ -182,6 +184,7 @@ are overridden in all cases by setting output format to `format2`.
 * `--oasv or --oasvlite`: Use ASV format for output data.
 * `--ocsv`: Use CSV format for output data.
 * `--ocsvlite`: Use CSV-lite format for output data.
+* `--odcf`: Use Debian control file (DCF) format for output data.
 * `--odkvp`: Use DKVP format for output data.
 * `--ojson`: Use JSON format for output data.
 * `--ojsonl`: Use JSON Lines format for output data.
@@ -219,7 +222,7 @@ See the flatten/unflatten doc page https://miller.readthedocs.io/en/latest/flatt
 ## Format-conversion keystroke-saver flags
 
 The letters `c`, `t`, `j`, `l`, `d`, `n`, `x`, `p`, `m`, and `y` refer to formats CSV, TSV, JSON, JSON Lines,
-DKVP, NIDX, XTAB, PPRINT, markdown, and YAML, respectively. Note that markdown format is available for
+DKVP, NIDX, XTAB, PPRINT, markdown, and YAML, respectively. DCF is also supported (use `--dcf` for DCF in and out). Note that markdown format is available for
 output only.
 
 | In \ out  | **CSV** | **TSV** | **JSON** | **JSONL** | **DKVP** | **NIDX** | **XTAB** | **PPRINT** | **Markdown** | **YAML** |
@@ -494,6 +497,7 @@ Notes about all other separators:
         Format   FS     PS     RS
         csv      ","    N/A    "\n"
         csvlite  ","    N/A    "\n"
+        dcf      N/A    N/A    N/A
         dkvp     ","    "="    "\n"
         gen      ","    N/A    "\n"
         json     N/A    N/A    N/A

docs/src/reference-main-separators.md

@@ -276,6 +276,7 @@ Notes:
 | [**TSV-lite**](file-formats.md#csvtsvasvusvetc)    | Default `\n` *  |  Default `\t`   | None     |
 | [**JSON**](file-formats.md#json)   | N/A; records are between `{` and `}` | Always `,`; not alterable    | Always `:`; not alterable |
 | [**YAML**](file-formats.md#yaml)   | N/A; documents separated by `---` or single array   | N/A; not alterable    | Always `:`; not alterable |
+| [**DCF**](file-formats.md#dcf-debian-control-file)   | N/A; paragraphs separated by blank lines   | N/A; not alterable    | Always `:`; not alterable |
 | [**DKVP**](file-formats.md#dkvp-key-value-pairs)   | Default `\n`    | Default `,`    | Default `=` |
 | [**NIDX**](file-formats.md#nidx-index-numbered-toolkit-style)   | Default `\n`    | Default space    | None     |
 | [**XTAB**](file-formats.md#xtab-vertical-tabular)   | Not used; records are separated by an extra FS    | `\n` *    | Default: space with repeats  |

docs/src/reference-main-separators.md.in

@@ -166,6 +166,7 @@ Notes:
 | [**TSV-lite**](file-formats.md#csvtsvasvusvetc)    | Default `\n` *  |  Default `\t`   | None     |
 | [**JSON**](file-formats.md#json)   | N/A; records are between `{` and `}` | Always `,`; not alterable    | Always `:`; not alterable |
 | [**YAML**](file-formats.md#yaml)   | N/A; documents separated by `---` or single array   | N/A; not alterable    | Always `:`; not alterable |
+| [**DCF**](file-formats.md#dcf-debian-control-file)   | N/A; paragraphs separated by blank lines   | N/A; not alterable    | Always `:`; not alterable |
 | [**DKVP**](file-formats.md#dkvp-key-value-pairs)   | Default `\n`    | Default `,`    | Default `=` |
 | [**NIDX**](file-formats.md#nidx-index-numbered-toolkit-style)   | Default `\n`    | Default space    | None     |
 | [**XTAB**](file-formats.md#xtab-vertical-tabular)   | Not used; records are separated by an extra FS    | `\n` *    | Default: space with repeats  |

go.mod

@@ -40,6 +40,9 @@ require (
 	github.com/google/pprof v0.0.0-20211214055906-6f57359322fd // indirect
 	github.com/kshedden/dstream v0.0.0-20190512025041-c4c410631beb // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	golang.org/x/crypto v0.40.0 // indirect
 	golang.org/x/tools v0.41.0 // indirect
 	gonum.org/v1/gonum v0.16.0 // indirect
+	pault.ag/go/debian v0.19.0 // indirect
+	pault.ag/go/topsort v0.1.1 // indirect
 )

go.sum

@@ -41,6 +41,8 @@ github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/
 github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
 github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
+golang.org/x/crypto v0.40.0 h1:r4x+VvoG5Fm+eJcxMaY8CQM7Lb0l1lsmjGBQ6s8BfKM=
+golang.org/x/crypto v0.40.0/go.mod h1:Qr1vMER5WyS2dfPHAlsOj01wgLbsyWtFn/aY+5+ZdxY=
 golang.org/x/sys v0.0.0-20211007075335-d3039528d8ac/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.41.0 h1:Ivj+2Cp/ylzLiEU89QhWblYnOE9zerudt9Ftecq2C6k=
@@ -58,3 +60,7 @@ gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+pault.ag/go/debian v0.19.0 h1:RUxCjScMbnlqFH5I+qsmyjZH8fXXtQ05rlkMJop3tjo=
+pault.ag/go/debian v0.19.0/go.mod h1:1LMojDAazlJ7cA5Ne6H2ZHD4hh3o8NRiW+MpvQRji2o=
+pault.ag/go/topsort v0.1.1 h1:L0QnhUly6LmTv0e3DEzbN2q6/FGgAcQvaEw65S53Bg4=
+pault.ag/go/topsort v0.1.1/go.mod h1:r1kc/L0/FZ3HhjezBIPaNVhkqv8L0UJ9bxRuHRVZ0q4=

man/manpage.txt

@@ -120,6 +120,17 @@
        | fox jumped          | Record 2: "1":"fox", "2":"jumped"
        +---------------------+
 
+       DCF: Debian control file format
+       +------------+
+       | apple: 1   |
+       | bat: 2     |
+       | cog: 3     |
+       |            |
+       | dish: 7    |
+       | egg: 8     |
+       | 3: flint   |
+       +------------+
+
 1mHELP OPTIONS0m
        Type 'mlr help {topic}' for any of the following:
        Essentials:
@@ -372,6 +383,8 @@
        --asv or --asvlite       Use ASV format for input and output data.
        --csv or -c or --c2c     Use CSV format for input and output data.
        --csvlite                Use CSV-lite format for input and output data.
+       --dcf                    Use Debian control file (DCF) format for input and
+                                output data.
        --dkvp or --d2d          Use DKVP format for input and output data.
        --gen-field-name         Specify field name for --igen. Defaults to "i".
        --gen-start              Specify start value for --igen. Defaults to 1.
@@ -380,6 +393,7 @@
        --iasv or --iasvlite     Use ASV format for input data.
        --icsv                   Use CSV format for input data.
        --icsvlite               Use CSV-lite format for input data.
+       --idcf                   Use Debian control file (DCF) format for input data.
        --idkvp                  Use DKVP format for input data.
        --igen                   Ignore input files and instead generate sequential
                                 numeric input using --gen-field-name, --gen-start,
@@ -403,6 +417,7 @@
        --oasv or --oasvlite     Use ASV format for output data.
        --ocsv                   Use CSV format for output data.
        --ocsvlite               Use CSV-lite format for output data.
+       --odcf                   Use Debian control file (DCF) format for output data.
        --odkvp                  Use DKVP format for output data.
        --ojson                  Use JSON format for output data.
        --ojsonl                 Use JSON Lines format for output data.
@@ -449,7 +464,7 @@
 1mFORMAT-CONVERSION KEYSTROKE-SAVER FLAGS0m
        As keystroke-savers for format-conversion you may use the following.
        The letters c, t, j, l, d, n, x, p, m, and y refer to formats CSV, TSV, JSON, JSON Lines,
-       DKVP, NIDX, XTAB, PPRINT, markdown, and YAML, respectively.
+       DKVP, NIDX, XTAB, PPRINT, markdown, and YAML, respectively. DCF is also supported (use --dcf for DCF in and out).
 
        | In\out   | CSV      | TSV      | JSON     | JSONL | DKVP  | NIDX  | XTAB  | PPRINT | Markdown | YAML   |
        +----------+----------+----------+----------+-------+-------+-------+-------+--------+----------+--------+
@@ -816,6 +831,7 @@
                Format   FS     PS     RS
                csv      ","    N/A    "\n"
                csvlite  ","    N/A    "\n"
+               dcf      N/A    N/A    N/A
                dkvp     ","    "="    "\n"
                gen      ","    N/A    "\n"
                json     N/A    N/A    N/A
@@ -3766,4 +3782,4 @@
        MIME Type for Comma-Separated Values (CSV) Files, the Miller docsite
        https://miller.readthedocs.io
 
-                                  2026-02-15                         4mMILLER24m(1)
+                                  2026-02-16                         4mMILLER24m(1)

man/mlr.1

@@ -2,12 +2,12 @@
 .\"     Title: mlr
 .\"    Author: [see the "AUTHOR" section]
 .\" Generator: ./mkman.rb
-.\"      Date: 2026-02-15
+.\"      Date: 2026-02-16
 .\"    Manual: \ \&
 .\"    Source: \ \&
 .\"  Language: English
 .\"
-.TH "MILLER" "1" "2026-02-15" "\ \&" "\ \&"
+.TH "MILLER" "1" "2026-02-16" "\ \&" "\ \&"
 .\" -----------------------------------------------------------------
 .\" * Portability definitions
 .\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -150,6 +150,17 @@ NIDX: implicitly numerically indexed (Unix-toolkit style)
 | the quick brown     | Record 1: "1":"the", "2":"quick", "3":"brown"
 | fox jumped          | Record 2: "1":"fox", "2":"jumped"
 +---------------------+
+
+DCF: Debian control file format
++------------+
+| apple: 1   |
+| bat: 2     |
+| cog: 3     |
+|            |
+| dish: 7    |
+| egg: 8     |
+| 3: flint   |
++------------+
 .fi
 .if n \{\
 .RE
@@ -461,6 +472,8 @@ are overridden in all cases by setting output format to `format2`.
 --asv or --asvlite       Use ASV format for input and output data.
 --csv or -c or --c2c     Use CSV format for input and output data.
 --csvlite                Use CSV-lite format for input and output data.
+--dcf                    Use Debian control file (DCF) format for input and
+                         output data.
 --dkvp or --d2d          Use DKVP format for input and output data.
 --gen-field-name         Specify field name for --igen. Defaults to "i".
 --gen-start              Specify start value for --igen. Defaults to 1.
@@ -469,6 +482,7 @@ are overridden in all cases by setting output format to `format2`.
 --iasv or --iasvlite     Use ASV format for input data.
 --icsv                   Use CSV format for input data.
 --icsvlite               Use CSV-lite format for input data.
+--idcf                   Use Debian control file (DCF) format for input data.
 --idkvp                  Use DKVP format for input data.
 --igen                   Ignore input files and instead generate sequential
                          numeric input using --gen-field-name, --gen-start,
@@ -492,6 +506,7 @@ are overridden in all cases by setting output format to `format2`.
 --oasv or --oasvlite     Use ASV format for output data.
 --ocsv                   Use CSV format for output data.
 --ocsvlite               Use CSV-lite format for output data.
+--odcf                   Use Debian control file (DCF) format for output data.
 --odkvp                  Use DKVP format for output data.
 --ojson                  Use JSON format for output data.
 --ojsonl                 Use JSON Lines format for output data.
@@ -554,7 +569,7 @@ See the flatten/unflatten doc page https://miller.readthedocs.io/en/latest/flatt
 .nf
 As keystroke-savers for format-conversion you may use the following.
 The letters c, t, j, l, d, n, x, p, m, and y refer to formats CSV, TSV, JSON, JSON Lines,
-DKVP, NIDX, XTAB, PPRINT, markdown, and YAML, respectively.
+DKVP, NIDX, XTAB, PPRINT, markdown, and YAML, respectively. DCF is also supported (use --dcf for DCF in and out).
 
 | In\eout   | CSV      | TSV      | JSON     | JSONL | DKVP  | NIDX  | XTAB  | PPRINT | Markdown | YAML   |
 +----------+----------+----------+----------+-------+-------+-------+-------+--------+----------+--------+
@@ -977,6 +992,7 @@ Notes about all other separators:
         Format   FS     PS     RS
         csv      ","    N/A    "\en"
         csvlite  ","    N/A    "\en"
+        dcf      N/A    N/A    N/A
         dkvp     ","    "="    "\en"
         gen      ","    N/A    "\en"
         json     N/A    N/A    N/A

pkg/cli/flatten_unflatten.go

@@ -61,7 +61,8 @@ package cli
 func DecideFinalFlatten(writerOptions *TWriterOptions) bool {
 	ofmt := writerOptions.OutputFileFormat
 	if writerOptions.AutoFlatten {
-		if ofmt != "json" {
+		// Preserve nested/array structure for formats that support it.
+		if ofmt != "json" && ofmt != "jsonl" && ofmt != "dcf" {
 			return true
 		}
 	}

pkg/cli/option_parse.go

@@ -787,6 +787,15 @@ var FileFormatFlagSection = FlagSection{
 			},
 		},
 
+		{
+			name: "--idcf",
+			help: "Use Debian control file (DCF) format for input data.",
+			parser: func(args []string, argc int, pargi *int, options *TOptions) {
+				options.ReaderOptions.InputFileFormat = "dcf"
+				*pargi += 1
+			},
+		},
+
 		{
 			name: "--inidx",
 			help: "Use NIDX format for input data.",
@@ -1021,6 +1030,15 @@ var FileFormatFlagSection = FlagSection{
 			},
 		},
 
+		{
+			name: "--odcf",
+			help: "Use Debian control file (DCF) format for output data.",
+			parser: func(args []string, argc int, pargi *int, options *TOptions) {
+				options.WriterOptions.OutputFileFormat = "dcf"
+				*pargi += 1
+			},
+		},
+
 		{
 			name: "--onidx",
 			help: "Use NIDX format for output data.",
@@ -1200,6 +1218,16 @@ var FileFormatFlagSection = FlagSection{
 			},
 		},
 
+		{
+			name: "--dcf",
+			help: "Use Debian control file (DCF) format for input and output data.",
+			parser: func(args []string, argc int, pargi *int, options *TOptions) {
+				options.ReaderOptions.InputFileFormat = "dcf"
+				options.WriterOptions.OutputFileFormat = "dcf"
+				*pargi += 1
+			},
+		},
+
 		{
 			name:     "--nidx",
 			help:     "Use NIDX format for input and output data.",
@@ -1252,7 +1280,7 @@ var FileFormatFlagSection = FlagSection{
 func FormatConversionKeystrokeSaverPrintInfo() {
 	fmt.Println(`As keystroke-savers for format-conversion you may use the following.
 The letters c, t, j, l, d, n, x, p, m, and y refer to formats CSV, TSV, JSON, JSON Lines,
-DKVP, NIDX, XTAB, PPRINT, markdown, and YAML, respectively.
+DKVP, NIDX, XTAB, PPRINT, markdown, and YAML, respectively. DCF is also supported (use --dcf for DCF in and out).
 
 | In\out   | CSV      | TSV      | JSON     | JSONL | DKVP  | NIDX  | XTAB  | PPRINT | Markdown | YAML   |
 +----------+----------+----------+----------+-------+-------+-------+-------+--------+----------+--------+

pkg/cli/separators.go

@@ -88,6 +88,7 @@ var defaultFSes = map[string]string{
 	"dkvp":     ",",
 	"json":     "N/A", // not alterable; not parameterizable in JSON format
 	"yaml":     "N/A",
+	"dcf":      "N/A",
 	"nidx":     " ",
 	"markdown": " ",
 	"pprint":   " ",
@@ -102,6 +103,7 @@ var defaultPSes = map[string]string{
 	"dkvp":     "=",
 	"json":     "N/A", // not alterable; not parameterizable in JSON format
 	"yaml":     "N/A",
+	"dcf":      "N/A",
 	"markdown": "N/A",
 	"nidx":     "N/A",
 	"pprint":   "N/A",
@@ -116,6 +118,7 @@ var defaultRSes = map[string]string{
 	"dkvp":     "\n",
 	"json":     "N/A", // not alterable; not parameterizable in JSON format
 	"yaml":     "N/A",
+	"dcf":      "N/A",
 	"markdown": "\n",
 	"nidx":     "\n",
 	"pprint":   "\n",
@@ -130,6 +133,7 @@ var defaultAllowRepeatIFSes = map[string]bool{
 	"dkvp":     false,
 	"json":     false,
 	"yaml":     false,
+	"dcf":      false,
 	"markdown": false,
 	"nidx":     false,
 	"pprint":   true,

pkg/input/record_reader_dcf.go

@@ -0,0 +1,198 @@
+package input
+
+import (
+	"io"
+	"strings"
+
+	"pault.ag/go/debian/control"
+
+	"github.com/johnkerl/miller/v6/pkg/cli"
+	"github.com/johnkerl/miller/v6/pkg/lib"
+	"github.com/johnkerl/miller/v6/pkg/mlrval"
+	"github.com/johnkerl/miller/v6/pkg/types"
+)
+
+// DCF list-valued field names (comma-separated in the format). These are
+// exposed as Miller arrays; all other fields remain strings.
+var dcfListFieldNames = map[string]bool{
+	"Depends":               true,
+	"Pre-Depends":           true,
+	"Recommends":            true,
+	"Suggests":              true,
+	"Enhances":              true,
+	"Breaks":                true,
+	"Conflicts":             true,
+	"Replaces":              true,
+	"Build-Depends":         true,
+	"Build-Depends-Indep":   true,
+	"Build-Conflicts":       true,
+	"Build-Conflicts-Indep": true,
+	"Built-Using":           true,
+}
+
+type RecordReaderDCF struct {
+	readerOptions   *cli.TReaderOptions
+	recordsPerBatch int64
+}
+
+func NewRecordReaderDCF(
+	readerOptions *cli.TReaderOptions,
+	recordsPerBatch int64,
+) (*RecordReaderDCF, error) {
+	return &RecordReaderDCF{
+		readerOptions:   readerOptions,
+		recordsPerBatch: recordsPerBatch,
+	}, nil
+}
+
+func (reader *RecordReaderDCF) Read(
+	filenames []string,
+	context types.Context,
+	readerChannel chan<- []*types.RecordAndContext,
+	errorChannel chan error,
+	downstreamDoneChannel <-chan bool,
+) {
+	if filenames != nil {
+		if len(filenames) == 0 {
+			handle, err := lib.OpenStdin(
+				reader.readerOptions.Prepipe,
+				reader.readerOptions.PrepipeIsRaw,
+				reader.readerOptions.FileInputEncoding,
+			)
+			if err != nil {
+				errorChannel <- err
+			} else {
+				reader.processHandle(handle, "(stdin)", &context, readerChannel, errorChannel, downstreamDoneChannel)
+			}
+		} else {
+			for _, filename := range filenames {
+				handle, err := lib.OpenFileForRead(
+					filename,
+					reader.readerOptions.Prepipe,
+					reader.readerOptions.PrepipeIsRaw,
+					reader.readerOptions.FileInputEncoding,
+				)
+				if err != nil {
+					errorChannel <- err
+				} else {
+					reader.processHandle(handle, filename, &context, readerChannel, errorChannel, downstreamDoneChannel)
+					handle.Close()
+				}
+			}
+		}
+	}
+	readerChannel <- types.NewEndOfStreamMarkerList(&context)
+}
+
+func (reader *RecordReaderDCF) processHandle(
+	handle io.Reader,
+	filename string,
+	context *types.Context,
+	readerChannel chan<- []*types.RecordAndContext,
+	errorChannel chan error,
+	downstreamDoneChannel <-chan bool,
+) {
+	context.UpdateForStartOfFile(filename)
+	recordsPerBatch := reader.recordsPerBatch
+
+	pr, err := control.NewParagraphReader(handle, nil)
+	if err != nil {
+		errorChannel <- err
+		return
+	}
+
+	recordsAndContexts := make([]*types.RecordAndContext, 0, recordsPerBatch)
+	i := int64(0)
+
+	for {
+		i++
+		if i%recordsPerBatch == 0 {
+			select {
+			case <-downstreamDoneChannel:
+				goto flush
+			default:
+			}
+		}
+
+		para, err := pr.Next()
+		if err != nil {
+			if err == io.EOF {
+				break
+			}
+			errorChannel <- err
+			return
+		}
+		if para == nil {
+			break
+		}
+
+		rec := dcfParagraphToRecord(para, reader.readerOptions.DedupeFieldNames)
+		if rec == nil {
+			// dedupe or other error already sent
+			return
+		}
+
+		context.UpdateForInputRecord()
+		recordsAndContexts = append(recordsAndContexts, types.NewRecordAndContext(rec, context))
+		if int64(len(recordsAndContexts)) >= recordsPerBatch {
+			readerChannel <- recordsAndContexts
+			recordsAndContexts = make([]*types.RecordAndContext, 0, recordsPerBatch)
+		}
+	}
+
+flush:
+	if len(recordsAndContexts) > 0 {
+		readerChannel <- recordsAndContexts
+	}
+}
+
+// splitCommaList splits a DCF comma-separated value and returns Miller Mlrval
+// array elements (trimmed, skipping empty).
+func splitCommaList(s string) []*mlrval.Mlrval {
+	parts := strings.Split(s, ",")
+	out := make([]*mlrval.Mlrval, 0, len(parts))
+	for _, p := range parts {
+		p = strings.TrimSpace(p)
+		if p == "" {
+			continue
+		}
+		out = append(out, mlrval.FromString(p))
+	}
+	return out
+}
+
+// dcfParagraphToRecord converts a control paragraph to a Miller record. List
+// fields (Depends, Build-Depends, etc.) become arrays; all other fields stay
+// strings. Uses para.Order to preserve field order. Returns nil on error (caller
+// must have sent on errorChannel).
+func dcfParagraphToRecord(para *control.Paragraph, dedupeFieldNames bool) *mlrval.Mlrmap {
+	rec := mlrval.NewMlrmapAsRecord()
+
+	// Preserve order from the DCF file when present.
+	keys := para.Order
+	if len(keys) == 0 {
+		for k := range para.Values {
+			keys = append(keys, k)
+		}
+	}
+
+	for _, k := range keys {
+		v, ok := para.Values[k]
+		if !ok {
+			continue
+		}
+
+		var mv *mlrval.Mlrval
+		if dcfListFieldNames[k] {
+			mv = mlrval.FromArray(splitCommaList(v))
+		} else {
+			mv = mlrval.FromString(v)
+		}
+
+		if _, err := rec.PutReferenceMaybeDedupe(k, mv, dedupeFieldNames); err != nil {
+			return nil
+		}
+	}
+
+	return rec
+}

pkg/input/record_reader_factory.go

@@ -30,6 +30,8 @@ func Create(readerOptions *cli.TReaderOptions, recordsPerBatch int64) (IRecordRe
 		return NewRecordReaderTSV(readerOptions, recordsPerBatch)
 	case "xtab":
 		return NewRecordReaderXTAB(readerOptions, recordsPerBatch)
+	case "dcf":
+		return NewRecordReaderDCF(readerOptions, recordsPerBatch)
 	case "gen":
 		return NewPseudoReaderGen(readerOptions, recordsPerBatch)
 	default:

pkg/lib/file_readers.go

@@ -2,7 +2,7 @@
 // Wrapper for os.Open which maps string filename to *os.File, which in turn
 // implements io.ReadCloser, and optional in turn wrapping that in a
 // gzip/zlib/bunzip2 reader. Shared across record-readers for all the various
-// input-file formats (CSV, JSON, XTAB, DKVP, NIDX, PPRINT) which Miller
+// input-file formats (CSV, JSON, XTAB, DKVP, NIDX, PPRINT, DCF) which Miller
 // supports.
 //
 // There are two ways of handling compressed data in the Miller Go port:

pkg/output/record_writer_dcf.go

@@ -0,0 +1,85 @@
+package output
+
+import (
+	"bufio"
+	"strings"
+
+	"github.com/johnkerl/miller/v6/pkg/cli"
+	"github.com/johnkerl/miller/v6/pkg/colorizer"
+	"github.com/johnkerl/miller/v6/pkg/mlrval"
+	"github.com/johnkerl/miller/v6/pkg/types"
+)
+
+type RecordWriterDCF struct {
+	writerOptions *cli.TWriterOptions
+}
+
+func NewRecordWriterDCF(writerOptions *cli.TWriterOptions) (*RecordWriterDCF, error) {
+	return &RecordWriterDCF{
+		writerOptions: writerOptions,
+	}, nil
+}
+
+func (writer *RecordWriterDCF) Write(
+	outrec *mlrval.Mlrmap,
+	_ *types.Context,
+	bufferedOutputStream *bufio.Writer,
+	outputIsStdout bool,
+) error {
+	if outrec == nil {
+		return nil
+	}
+	if outrec.IsEmpty() {
+		bufferedOutputStream.WriteString("\n")
+		return nil
+	}
+
+	for pe := outrec.Head; pe != nil; pe = pe.Next {
+		valueStr := dcfValueString(pe.Value)
+		keyStr := colorizer.MaybeColorizeKey(pe.Key, outputIsStdout)
+		valueStr = colorizer.MaybeColorizeValue(valueStr, outputIsStdout)
+		writeDCFField(bufferedOutputStream, keyStr, valueStr)
+	}
+	bufferedOutputStream.WriteString("\n")
+	return nil
+}
+
+// dcfValueString returns the string form of a field value for DCF output.
+// Arrays are joined with ", " to match list fields (Depends, etc.).
+func dcfValueString(mv *mlrval.Mlrval) string {
+	if mv == nil {
+		return ""
+	}
+	if mv.IsArray() {
+		arr := mv.GetArray()
+		if arr == nil || len(arr) == 0 {
+			return ""
+		}
+		parts := make([]string, 0, len(arr))
+		for _, el := range arr {
+			if el != nil {
+				parts = append(parts, el.String())
+			}
+		}
+		return strings.Join(parts, ", ")
+	}
+	return mv.String()
+}
+
+// writeDCFField writes one "Key: value" line, folding on newlines per DCF:
+// continuation lines start with a single space.
+func writeDCFField(b *bufio.Writer, key, value string) {
+	lines := strings.Split(value, "\n")
+	for i, line := range lines {
+		if i == 0 {
+			b.WriteString(key)
+			b.WriteString(": ")
+			b.WriteString(line)
+			b.WriteString("\n")
+		} else {
+			b.WriteString(" ")
+			b.WriteString(line)
+			b.WriteString("\n")
+		}
+	}
+}

pkg/output/record_writer_factory.go

@@ -20,6 +20,8 @@ func Create(writerOptions *cli.TWriterOptions) (IRecordWriter, error) {
 		return NewRecordWriterJSONLines(writerOptions)
 	case "yaml":
 		return NewRecordWriterYAML(writerOptions)
+	case "dcf":
+		return NewRecordWriterDCF(writerOptions)
 	case "md":
 		return NewRecordWriterMarkdown(writerOptions)
 	case "markdown":

pkg/terminals/help/entry.go

@@ -447,6 +447,17 @@ NIDX: implicitly numerically indexed (Unix-toolkit style)
 | the quick brown     | Record 1: "1":"the", "2":"quick", "3":"brown"
 | fox jumped          | Record 2: "1":"fox", "2":"jumped"
 +---------------------+
+
+DCF: Debian control file format
++------------+
+| apple: 1   |
+| bat: 2     |
+| cog: 3     |
+|            |
+| dish: 7    |
+| egg: 8     |
+| 3: flint   |
++------------+
 `)
 }
 

test/cases/io-dcf/0001/cmd

@@ -0,0 +1 @@
+mlr --itsv --rs lf --odcf cat test/input/simple.tsv

test/cases/io-dcf/0001/expout

@@ -0,0 +1,30 @@
+a: pan
+b: pan
+i: 1
+x: 2
+y: 0.98994500
+
+a: eks
+b: pan
+i: 2
+x: 1
+y: 0.77515900
+
+a: wye
+b: wye
+i: 3
+x: 1
+y: 0.76164200
+
+a: eks
+b: wye
+i: 4
+x: 5
+y: 0.32293400
+
+a: wye
+b: pan
+i: 5
+x: 5
+y: 0.44828300
+

test/cases/io-dcf/0002/cmd

@@ -0,0 +1 @@
+mlr --icsv --odcf cat ${CASEDIR}/input

test/cases/io-dcf/0002/expout

@@ -0,0 +1,4 @@
+a: 1
+b: 2|3
+c: 4
+

test/cases/io-dcf/0002/input

@@ -0,0 +1,2 @@
+a,b,c
+1,2|3,4

test/cases/io-dcf/0003/cmd

@@ -0,0 +1 @@
+mlr --idcf --odcf cat test/input/test.dcf

test/cases/io-dcf/0003/expout

@@ -0,0 +1,10 @@
+Package: foo
+Version: 1.0
+Depends: libc6 (>= 2.0), libfoo (>= 1.2)
+Description: A test package.
+
+Package: bar
+Version: 2.0
+Recommends: foo
+Description: Another package.
+

test/cases/io-dcf/dcf-input/cmd

@@ -0,0 +1 @@
+mlr --idcf --ojson cat test/input/test.dcf

test/cases/io-dcf/dcf-input/expout

@@ -0,0 +1,14 @@
+[
+{
+  "Package": "foo",
+  "Version": "1.0",
+  "Depends": ["libc6 (>= 2.0)", "libfoo (>= 1.2)"],
+  "Description": "A test package."
+},
+{
+  "Package": "bar",
+  "Version": "2.0",
+  "Recommends": ["foo"],
+  "Description": "Another package."
+}
+]

test/input/test.dcf

@@ -0,0 +1,9 @@
+Package: foo
+Version: 1.0
+Depends: libc6 (>= 2.0), libfoo (>= 1.2)
+Description: A test package.
+
+Package: bar
+Version: 2.0
+Recommends: foo
+Description: Another package.