Wait until one of the specified connections or processes produce standard output or error, terminates, or a timeout occurs.
A list of connection objects or
Integer scalar, a timeout for the polling, in milliseconds. Supply -1 for an infitite timeout, and 0 for not waiting at all.
A list of character vectors of length one or three.
There is one list element for each connection/process, in the same
order as in the input list. For connections the result is a single
string scalar. For processes the character vectors' elements are named
process. Possible values for each individual
See details about these below.
process refers to the poll connection,
poll_connection argument of the
nopipe means that the stdout or stderr from this process was not
ready means that the connection or the stdout or stderr from this
process are ready to read from. Note that end-of-file on these
outputs also triggers
timeout': the connections or processes are not ready to read from and a timeout happened.
closed: the connection was already closed, before the polling
silent: the connection is not ready to read from, but another
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# Different commands to run for windows and unix cmd1 <- switch( .Platform$OS.type, "unix" = c("sh", "-c", "sleep 1; ls"), c("cmd", "/c", "ping -n 2 127.0.0.1 && dir /b") ) cmd2 <- switch( .Platform$OS.type, "unix" = c("sh", "-c", "sleep 2; ls 1>&2"), c("cmd", "/c", "ping -n 2 127.0.0.1 && dir /b 1>&2") ) ## Run them. p1 writes to stdout, p2 to stderr, after some sleep p1 <- process$new(cmd1, cmd1[-1], stdout = "|") p2 <- process$new(cmd2, cmd2[-1], stderr = "|") ## Nothing to read initially poll(list(p1 = p1, p2 = p2), 0) ## Wait until p1 finishes. Now p1 has some output p1$wait() poll(list(p1 = p1, p2 = p2), -1) ## Close p1's connection, p2 will have output on stderr, eventually close(p1$get_output_connection()) poll(list(p1 = p1, p2 = p2), -1) ## Close p2's connection as well, no nothing to poll close(p2$get_error_connection()) poll(list(p1 = p1, p2 = p2), 0)
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