R - Connection (Stream)

About

Data are read in using connection interfaces:

file,
gzfile, (a file compressed with gzip)
bzfile, (a file compressed with bzip2)
url (an HTTP location)

showConnections

showConnections(all = TRUE)

description class            mode text   isopen   can read can write
0 "stdin"     "terminal"       "r"  "text" "opened" "yes"    "no"     
1 "stdout"    "terminal"       "w"  "text" "opened" "no"     "yes"    
2 "stderr"    "terminal"       "w"  "text" "opened" "no"     "yes"    
3 "letters"   "textConnection" "r"  "text" "opened" "yes"    "no"

where:

stdin, stdout and stderr are the standard streams
class can be terminal or textConnection

getConnection

getConnection(what)

where:

what is a row number of the showconnections output.

closeAllConnections

closeAllConnections()

stdin(), stdout() and stderr()

stdin(), stdout() and stderr() return connection objects.

stdin() refers to the “console” and not to the C-level “stdin” of the process. To access to the C-level file stream “stdin”, use file(“stdin”).

How to

know if the connection is connected to a terminal

The isatty function returns true if the connection is one of the class “terminal” connections and it is apparently connected to a terminal, otherwise false. This may not be reliable in embedded applications, including GUI consoles.

> c(isatty(stdin()), isatty(stdout()), isatty(stderr()))
[1] FALSE FALSE FALSE