R: Read and Write Data in DCF Format

dcf {base} | R Documentation

## Read and Write Data in DCF Format

### Description

Reads or writes an R object from/to a file in Debian Control File format.

### Usage

    read.dcf(file, fields=NULL)
    write.dcf(x, file = "", append = FALSE,
              indent = 0.1 * getOption("width"),
              width = 0.9 * getOption("width"))

### Arguments

`file` | either a character string naming a file or a connection. `""` indicates output to the console.
`fields` | Fields to read from the DCF file. Default is to read all fields.
`x` | the object to be written, typically a data frame. If not, it is attempted to coerce `x` to a data frame.
`append` | logical. If `TRUE`, the output is appended to the file. If `FALSE`, any existing file of the name is destroyed.
`indent` | a positive integer specifying the indentation for continuation lines in output entries.
`width` | a positive integer giving the target column for wrapping lines in the output.

### Details

DCF is a simple format for storing databases in plain text files that can easily be directly read and written by humans. DCF is used in various places to store R system information, like descriptions and contents of packages.

The DCF rules as implemented in R are:

1. A database consists of one or more records, each with one or more named fields. Not every record must contain each field.
2. Regular lines start with a non-whitespace character.
3. Regular lines are of form `tag:value`, i.e., have a name tag and a value for the field, seperated by `:` (only the first `:` counts). The value can be empty (=whitespace only).
4. Lines starting with whitespace are continuation lines (to the preceding field) if at least one character in the line is non-whitespace.
5. Records are seperated by one or more empty (=whitespace only) lines.

`read.dcf` returns a character matrix with one line per record and one column per field. Leading and trailing whitespace of field values is ignored. If a tag name is specified, but the corresponding value is empty, then an empty string of length 0 is returned. If the tag name of a fields is never used in a record, then `NA` is returned.

### See Also

`write.table`.

### Examples

    ## Create a reduced version of the `CONTENTS' file in package `eda'
    x <- read.dcf(file = system.file("CONTENTS", package = "eda"),
                   fields = c("Entry", "Description"))
    write.dcf(x)

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