Processx connections
These functions are currently experimental and will change in the future. Note that processx connections are not compatible with R's built-in connection system.
conn_create_fd(fd, encoding = "", close = TRUE) conn_create_pipepair(encoding = "", nonblocking = c(TRUE, FALSE)) conn_read_chars(con, n = -1) ## S3 method for class 'processx_connection' conn_read_chars(con, n = -1) processx_conn_read_chars(con, n = -1) conn_read_lines(con, n = -1) ## S3 method for class 'processx_connection' conn_read_lines(con, n = -1) processx_conn_read_lines(con, n = -1) conn_is_incomplete(con) ## S3 method for class 'processx_connection' conn_is_incomplete(con) processx_conn_is_incomplete(con) conn_write(con, str, sep = "\n", encoding = "") ## S3 method for class 'processx_connection' conn_write(con, str, sep = "\n", encoding = "") processx_conn_write(con, str, sep = "\n", encoding = "") conn_create_file(filename, read = NULL, write = NULL) conn_set_stdout(con, drop = TRUE) conn_set_stderr(con, drop = TRUE) conn_get_fileno(con) conn_disable_inheritance() ## S3 method for class 'processx_connection' close(con, ...) processx_conn_close(con, ...) is_valid_fd(fd)
fd |
Integer scalar, a Unix file descriptor. |
encoding |
Encoding of the readable connection when reading. |
close |
Whether to close the OS file descriptor when closing
the connection. Sometimes you want to leave it open, and use it again
in a |
nonblocking |
Whether the writeable and the readable ends of the pipe should be non-blocking connections. |
con |
Processx connection object. |
n |
Number of characters or lines to read. -1 means all available characters or lines. |
str |
Character or raw vector to write. |
sep |
Separator to use if |
filename |
File name. |
read |
Whether the connection is readable. |
write |
Whethe the connection is writeable. |
drop |
Whether to close the original stdout/stderr, or keep it open and return a connection to it. |
... |
Extra arguments, for compatibility with the |
conn_create_fd() creates a connection from a file descriptor.
conn_create_pipepair() creates a pair of connected connections, the
first one is writeable, the second one is readable.
conn_read_chars() reads UTF-8 characters from the connections. If the
connection itself is not UTF-8 encoded, it re-encodes it.
conn_read_lines() reads lines from a connection.
conn_is_incomplete() returns FALSE if the connection surely has no
more data.
conn_write() writes a character or raw vector to the connection.
It might not be able to write all bytes into the connection, in which
case it returns the leftover bytes in a raw vector. Call conn_write()
again with this raw vector.
conn_create_file() creates a connection to a file.
conn_set_stdout() set the standard output of the R process, to the
specified connection.
conn_set_stderr() set the standard error of the R process, to the
specified connection.
conn_get_fileno() return the integer file desciptor that belongs to
the connection.
conn_disable_inheritance() can be called to disable the inheritance
of all open handles. Call this function as soon as possible in a new
process to avoid inheriting the inherited handles even further.
The function is best effort to close the handles, it might still leave
some handles open. It should work for stdin, stdout and stderr,
at least.
is_valid_fd() returns TRUE if fd is a valid open file
descriptor. You can use it to check if the R process has standard
input, output or error. E.g. R processes running in GUI (like RGui)
might not have any of the standard streams available.
If a stream is redirected to the null device (e.g. in a callr subprocess), that is is still a valid file descriptor.
is_valid_fd(0L) # stdin is_valid_fd(1L) # stdout is_valid_fd(2L) # stderr
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