# R: Send R Output to a File

sink {base} | R Documentation

## Send R Output to a File

### Description

`sink` diverts R output to a connection.

`sink.number()` reports how many diversions are in use.

`sink.number(type = "message")` reports the number of the connection currently being used for error messages.

### Usage

    sink(file = NULL, append = FALSE, type = c("output", "message"),
         split = FALSE)

    sink.number(type = c("output", "message"))

### Arguments

`file` | a connection or a character string naming the file to write to, or `NULL` to stop sink-ing.
`append` | logical. If `TRUE`, output will be appended to `file`; otherwise, it will overwrite the contents of `file`.
`type` | character. Either the output stream or the messages stream.
`split` | logical: if `TRUE`, output will be sent to the new sink and to the current output stream, like the Unix program `tee`.

### Details

`sink` diverts R output to a connection. If `file` is a character string, a file connection with that name will be established for the duration of the diversion.

Normal R output (to connection `stdout))` is diverted by the default `type = "output"`. Only prompts and (most) messages continue to appear on the console. Messages sent to `stdout()` (including those from `message`, `warning` and `stop`) can be diverted by `sink(type = "message")` (see below).

`sink()` or `sink(file=NULL)` ends the last diversion (of the specified type). There is a stack of diversions for normal output, so output reverts to the previous diversion (if there was one). The stack is of up to 21 connections (20 diversions).

If `file` is a connection it will be opened if necessary.

Sink-ing the messages stream should be done only with great care. For that stream `file` must be an already open connection, and there is no stack of connections.

### Value

`sink` returns `NULL`.
For `sink.number()` the number (0, 1, 2, ...) of diversions of output in place.
For `sink.number("message")` the connection number used for messages, 2 if no diversion has been used.

### Warning

Don't use a connection that is open for `sink` for any other purpose. The software will stop you closing one such inadvertently.

Do not sink the messages stream unless you understand the source code implementing it and hence the pitfalls.

### Note

`sink(split = TRUE)` is only available on systems which support the C99 function `va_copy` (or under the name `__va_copy`), but we know of no current systems which do not.

### References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.

Chambers, J. M. (1998) Programming with Data. A Guide to the S Language. Springer.

### See Also

`capture.output`

### Examples

    sink("sink-examp.txt")
    i <- 1:10
    outer(i, i, "*")
    sink()
    unlink("sink-examp.txt")
    ## Not run:
    ## capture all the output to a file.
    zz <- file("all.Rout", open="wt")
    sink(zz)
    sink(zz, type="message")
    try(log("a"))
    ## back to the console
    sink(type="message")
    sink()
    try(log("a"))
    ## End(Not run)

[Package base version 2.6.0 Index]