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. For `read.dcf` this can name a `gzip`-compressed file.
`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:

A database consists of one or more records, each with one or more named fields. Not every record must contain each field, a field may appear only once in a record.
Regular lines start with a non-whitespace character.
Regular lines are of form tag:value, i.e., have a name tag and a value for the field, separated by : (only the first : counts). The value can be empty (=whitespace only).
Lines starting with whitespace are continuation lines (to the preceding field) if at least one character in the line is non-whitespace.
Records are separated 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. If there are multiple records with the same tag name, the last one encountered is returned. Malformed lines are ignored (with a warning).

Examples

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