pstream: Open a pipe stream object

In thk686/pipestreamr: Non-blocking IO over stdin, stdout and stderr

Description

Opens a set of pipes to stdin, stdout and stderr on the specified process.

Usage

pstream(command, args = "", read_formatter = function(x) x,
  write_formatter = function(x) as.character(x), bufsz = 1024,
  max_reads = 1024)

set_read_formatter(stream, func)

set_write_formatter(stream, func)

set_buffer_size(stream, bufsz)

set_max_reads(stream, max_reads)

pstream_close(stream, wait = 10)

## S3 method for class 'pstream'
close(con, ...)

## S3 method for class 'pstream'
open(con, ...)

send_eof(stream)

signal(stream, signal = 15, group = FALSE)

Arguments

command	the program to run
args	a vector of argument strings
read_formatter	formatter function when reading
write_formatter	formatter function when writing
bufsz	size of the read buffer
max_reads	maximum number of buffer fills
stream	a pstream object
func	a formatter function
wait	number of seconds to wait before sending the kill signal
con	a pstream object
...	ignored
signal	the POSIX signal number (see kill -l)
group	signal the entire process group?

Details

Closing a stream will wait until the spawned process completes. This can hang your session if the process is not well-behaved. You should manually end the proces if possible. pstream_close will check whether the program has exited. If it is still running, EOF is sent. The process is then checked for wait seconds. If the process does not exit during that period, then SIGTERM signal is sent. If after another round of waiting, the process has not existed, it is then sent the SIGKILL signal. After that, the stream is manually closed.

Note

Pipe stream objects are not compatible with R connection objects. (See pstream_input_con.) However, open and close methods are defined for convenience. close calls pstream_close. open will reopen a closed pstream object.

Examples

x = pstream("R")
status(x)
read_stderr(x)
pstream_close(x)

x = pstream("R", "--vanilla")
read_stdout(x)
write_stdin(x, "R.Version()[[1]]")
read_stdout(x)
send_eof(x); Sys.sleep(1)
status(x)

x = pstream("R", "--vanilla")
status(x)
signal(x); Sys.sleep(1)
status(x)

x = pstream("R", "--vanilla")
status(x)
close(x)
status(x)

wf = function(x) "dir()"
rf = function(x) "Boo!"
x = pstream("R", "--vanilla --slave", rf, wf)
write_stdin(x, "q()")
read_stdout(x)
close(x)

thk686/pipestreamr documentation built on May 31, 2019, 10:43 a.m.