readBin {base} | R Documentation

## Transfer Binary Data To and From Connections

### Description

Read binary data from a connection, or write binary data to a connection.

### Usage

    readBin(con, what, n = 1, size = NA, endian = .Platform$endian)
    writeBin(object, con, size = NA, endian = .Platform$endian)

### Arguments

`con` | A connection object or a character string.
`what` | Either an object whose mode will give the mode of the vector to be read, or a character vector of length one describing the mode: one of `"numeric", "double", "integer", "int", "logical", "complex", "character"`.
`n` | integer. The (maximal) number of records to be read. You can use an over-estimate here, but not too large as storage is reserved for `n` items.
`size` | integer. The number of bytes per element in the byte stream. The default, `NA`, uses the natural size. Size changing is not supported for complex vectors.
`endian` | The endian-ness (`"big"` or `"little"` of the target system for the file. Using `"swap"` will force swapping endian-ness.
`object` | An R object to be written to the connection.

### Details

If the `con` is a character string, the functions call `file` to obtain an file connection which is opened for the duration of the function call.

If the connection is open it is read/written from its current position. If it is not open, it is opened for the duration of the call and then closed again.

If `size` is specified and not the natural size of the object, each element of the vector is coerced to an appropriate type before being written or as it is read. Possible sizes are 1, 2, 4 and possibly 8 for integer or logical vectors, and 4, 8 and possibly 12/16 for numeric vectors. (Note that coercion occurs as signed types.) Changing sizes is unlikely to preserve `NA`s, and the extended precision sizes are unlikely to be portable across platforms.

### Value

For `readBin`, a vector of appropriate mode and the number of items read (which might be less than `n`).
For `writeBin`, none.

### Note

Integer read/writes of size 8 will be available if either C type `long` is of size 8 bytes or C type `long long` exists and is of size 8 bytes.

Real read/writes of size `sizeof(long double)` (usually 12 or 16 bytes) will be available only if that type is available and different from `double`.

### See Also

`connection`, `readLines`, `writeLines`

### Examples

    zz <- file("testbin", "wb")
    writeBin(1:10, zz)
    writeBin(pi, zz, endian="swap")
    writeBin(pi, zz, size=4)
    writeBin(pi^2, zz, size=4, endian="swap")
    writeBin(pi+3i, zz)
    writeBin("A test of a connection", zz)
    z <- paste("A very long string", 1:100, collapse=" + ")
    writeBin(z, zz)
    close(zz)

    zz <- file("testbin", "rb")
    readBin(zz, integer(), 4)
    readBin(zz, integer(), 6)
    readBin(zz, numeric(), 1, endian="swap")
    readBin(zz, numeric(), size=4)
    readBin(zz, numeric(), size=4, endian="swap")
    readBin(zz, complex(), 1)
    readBin(zz, character(), 1)
    z2 <- readBin(zz, character(), 1)
    close(zz)
    unlink("testbin")
    stopifnot(z2 == z)