Evaluate an R expression while temporarily diverting output

Evaluate an R expression while temporarily diverting output.

withSink(expr, file, append=FALSE, type=c("output", "message"), substitute=TRUE,
  envir=parent.frame())

Arguments

expr

The R expression to be evaluated.

file

A writable connection or a character string naming the file to write to.

append

If TRUE, the diverted output is appended to the file, otherwise not.

type

A character string specifying whether to divert output sent to the standard output or the standard error. See sink() for details.

substitute

If TRUE, argument expr is substitute():ed, otherwise not.

envir

The environment in which the expression should be evaluated.

Value

Returns the results of the expression evaluated.

Details

Upon exit (also on errors), this function will close the requested "sink". If additional sinks (of any type) where also opened during the evaluation, those will also be closed with a warning.

Author

Henrik Bengtsson

See also

Internally, sink() is used to divert any output.

Examples

# Divert standard output
pathname <- tempfile(fileext=".output.txt")
res <- withSink(file=pathname, {
  print(letters)
})
mcat(readLines(pathname), sep="\n")
#>  [1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q" "r" "s"
#> [20] "t" "u" "v" "w" "x" "y" "z"


# Divert standard error/messages
pathname <- tempfile(fileext=".message.txt")
res <- withSink(file=pathname, type="message", {
  mprint(LETTERS)
})
#>  [1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S"
#> [20] "T" "U" "V" "W" "X" "Y" "Z"
mcat(readLines(pathname), sep="\n")
#>