The R Project SVN R

% File src/library/utils/man/changedFiles.Rd

% Part of the R package, https://www.R-project.org

% Copyright 2013 R Core Team

% Distributed under GPL 2 or later

\name{changedFiles}

\alias{fileSnapshot}

\alias{changedFiles}

\alias{print.changedFiles}

\alias{print.fileSnapshot}

\title{Detect which Files Have Changed}

\description{

\code{fileSnapshot} takes a snapshot of a selection of files,

recording summary information about each.  \code{changedFiles}

compares two snapshots, or compares one snapshot to the current state

of the file system.  The snapshots need not be the same directory;

this could be used to compare two directories.

}

\usage{

fileSnapshot(path = ".", file.info = TRUE, timestamp = NULL, 

	    md5sum = FALSE, digest = NULL, full.names = length(path) > 1,

	    ...) 

changedFiles(before, after, path = before$path, timestamp = before$timestamp, 

	    check.file.info = c("size", "isdir", "mode", "mtime"), 

	    md5sum = before$md5sum, digest = before$digest, 

	    full.names = before$full.names, ...)

\S3method{print}{fileSnapshot}(x, verbose = FALSE, ...)

\S3method{print}{changedFiles}(x, verbose = FALSE, ...) 

} 

\arguments{ 

\item{path}{character vector; the path(s) to record. }

\item{file.info}{logical; whether to record \code{\link{file.info}}

values for each file.

}  

\item{timestamp}{character string or \code{NULL}; the name of a file

to write at the time the snapshot is taken.  This gives a quick test

for modification, but may be unreliable; see the Details. }

\item{md5sum}{logical; whether MD5 summaries of each file should be

taken as part of the snapshot. }

\item{digest}{a function or \code{NULL}; a function with header

\code{function(filename)} which will take a vector of filenames and

produce a vector of values of the same length, or a matrix with that

number of rows. }

\item{full.names}{logical; whether full names (as in

\code{\link{list.files}}) should be recorded. Must be \code{TRUE} if

\code{length(path) > 1}. }

\item{\dots}{ additional parameters to pass to

\code{\link{list.files}} to control the set of files in the snapshots.

}

\item{before, after}{objects produced by \code{fileSnapshot}; two

snapshots to compare.  If \code{after} is missing, a new snapshot of

the current file system will be produced for comparison, using

arguments recorded in \code{before} as defaults. }

\item{check.file.info}{character vector; which columns from

\code{\link{file.info}} should be compared. }

\item{x}{the object to print. }

\item{verbose}{logical; whether to list all data when printing. }

}

\details{

The \code{fileSnapshot} function uses \code{\link{list.files}} to

obtain a list of files, and depending on the \code{file.info},

\code{md5sum}, and \code{digest} arguments, records information about

each file.

The \code{changedFiles} function compares two snapshots. 

If the \code{timestamp} argument to \code{fileSnapshot} is length 1, a

file with that name is created. If it is length 1 in

\code{changedFiles}, the \code{\link{file_test}} function is used to

compare the age of all files common to both \code{before} and

\code{after} to it.  This test may be unreliable:  it compares the

current modification time of the \code{after} files to the timestamp;

that may not be the same as the modification time when the

\code{after} snapshot was taken.  It may also give incorrect results

if the clock on the file system holding the timestamp differs from the

one holding the snapshot files.

If the \code{check.file.info} argument contains a non-empty character

vector, the indicated columns from the result of a call to

\code{\link{file.info}} will be compared.

If \code{md5sum} is \code{TRUE}, \code{fileSnapshot} will call the

\code{tools::\link{md5sum}} function to record the 32 byte MD5

checksum for each file, and \code{changedFiles} will compare the

values.  The \code{digest} argument allows users to provide their own

digest function.

}

\value{

\code{fileSnapshot} returns an object of class \code{"fileSnapshot"}.

This is a list containing the fields 

\item{info}{a data frame whose rownames are the filenames, and whose

columns contain the requested snapshot data} 

\item{path}{the normalized \code{path} from the call} 

\item{timestamp, file.info, md5sum, digest, full.names}{a record of

the other arguments from the call} 

\item{args}{other arguments passed via \code{...} to

\code{\link{list.files}}.}

\code{changedFiles} produces an object of class \code{"changedFiles"}.

This is a list containing

\item{added, deleted, changed, unchanged}{character vectors of

filenames from the before and after snapshots, with obvious meanings}

\item{changes}{a logical matrix with a row for each common file, and a

column for each comparison test. \code{TRUE} indicates a change in

that test.}

\code{\link{print}} methods are defined for each of these types.  The

\code{\link{print}} method for \code{"fileSnapshot"} objects

displays the arguments used to produce them, while the one for

\code{"changedFiles"} displays the \code{added}, \code{deleted} and

\code{changed} fields if non-empty, and a submatrix of the

\code{changes} matrix containing all of the \code{TRUE} values.

}

\author{

Duncan Murdoch, using suggestions from Karl Millar and others.

}

\seealso{

\code{\link{file.info}}, \code{\link{file_test}}, \code{\link{md5sum}}.

}

\examples{

# Create some files in a temporary directory

dir <- tempfile()

dir.create(dir)

writeBin(1L, file.path(dir, "file1"))

writeBin(2L, file.path(dir, "file2"))

dir.create(file.path(dir, "dir"))

# Take a snapshot

snapshot <- fileSnapshot(dir, timestamp = tempfile("timestamp"), md5sum=TRUE)

# Change one of the files.

writeBin(3L:4L, file.path(dir, "file2"))

# Display the detected changes.  We may or may not see mtime change...

changedFiles(snapshot)

changedFiles(snapshot)$changes

}

\keyword{utilities}

\keyword{file}