readwrite: Communicating with a Child Process
In subprocess: Manage Sub-Processes in R

Description Usage Arguments Format Details Value

process_read() reads data from one of the child process' streams, standard output or standard error output, and returns it as a character vector.

process_write() writes data into child's standard input stream.

process_close_input() closes the write end of the pipe whose read end is the standard input stream of the child process. This is a standard way to gracefully request the child process to exit.

PIPE_STDOUT: read from child's standard output.

PIPE_STDERR: read from child's standard error output.

PIPE_BOTH: read from both child's output streams: standard output and standard error output.

process_read(handle, pipe = PIPE_BOTH, timeout = TIMEOUT_IMMEDIATE,
  flush = TRUE)

process_write(handle, message)

process_close_input(handle)

PIPE_STDOUT

PIPE_STDERR

PIPE_BOTH

`handle`	Process handle obtained from `spawn_process`.
`pipe`	Output stream identifier: `PIPE_STDOUT`, `PIPE_STDERR` or `PIPE_BOTH`.
`timeout`	Optional timeout in milliseconds.
`flush`	If there is any data within the given `timeout` try again with `timeout=0` until C buffer is empty.
`message`	Input for the child process.

PIPE_STDOUT, PIPE_STDERR and PIPE_BOTH are single character values.

If flush=TRUE in process_read() then the invocation of the underlying read() system-call will be repeated until the pipe buffer is empty.

If pipe is set to either PIPE_STDOUT or PIPE_STDERR, the returned value is a single list with a single key, stdout or stderr, respectively. If pipe is set to PIPE_BOTH the returned list contains both keys. Values in the list are character vectors of 0 or more elements, lines read from the respective output stream of the child process.

For details on timeout see terminating.

process_read returns a list which contains either of or both keys: stdout and stderr; the value is in both cases a character vector which contains lines of child's output.

process_write returns the number of characters written.

subprocess documentation built on May 2, 2019, 4:04 p.m.