sink {base} | R Documentation

## Send R Output to a File

### Description

`sink` diverts R output to a connection (and stops such diversions).

`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 writable 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 string. Either the output stream or the messages stream. The name will be partially matched so can be abbreviated.
`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 (and must be used again to finish such a diversion, see below!). 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 `stderr()` (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 (in `"wt"` mode) and closed once it is removed from the stack of diversions.

`split = TRUE` only splits R output (via `Rvprintf`) and the default output from `writeLines`: it does not split all output that might be sent to `stdout()`.

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.

If `file` is a character string, the file will be opened using the current encoding. If you want a different encoding (e.g., to represent strings which have been stored in UTF-8), use a `file` connection — but some ways to produce R output will already have converted such strings to the current encoding.

### 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

Do not 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.

### 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()

    ## capture all the output to a file.
    zz <- file("all.Rout", open = "wt")
    sink(zz)
    sink(zz, type = "message")
    try(log("a"))
    ## revert output back to the console -- only then access the file!
    sink(type = "message")
    sink()
    file.show("all.Rout")

[Package base version 3.3.2 Index]