shell {base} | R Documentation |
shell
runs the command specified by cmd
, usually under
a shell.
shell(cmd, shell, flag = "/c", intern = FALSE, wait = TRUE, translate = FALSE, mustWork = FALSE, ...)
cmd |
the system command to be invoked, as a string. |
shell |
a string giving the name of the shell to be used, or
NULL (no shell). If missing, a suitable shell is chosen:
see ‘Details’. |
flag |
the switch to run a command under the shell. If the
shell is bash or tcsh the default is changed to
"-c" . |
intern |
a logical, indicates whether to make the output of the command an R object. |
wait |
should the R interpreter wait for the command to finish?
The default is to wait, and the interpreter will always wait if
intern = TRUE . |
translate |
If TRUE , "/" in cmd is
translated to "\" . |
mustWork |
a logical; if TRUE failure to run the command
will give an R error. |
... |
additional arguments to system . |
If no shell
is specified, the environment variables
R_SHELL
, SHELL
and COMSPEC
are tried in turn:
COMSPEC
should always succeed. Using shell=NULL
invokes the command cmd
directly, in which case an extension
of .exe
is assumed. It is possible to use batch files
directly if their extension is given: Windows (rather than R) then
chooses a shell.
See system
for fuller details: shell
is a more
user-friendly wrapper for system
. To make use of Windows
file associations, use shell.exec
.
If intern=TRUE
, a character vector giving the output of the
command, one line per character string, or an error message if the
command could not be run.
If intern=FALSE
, the return value is an error code, given the
invisible attribute (so needs to be printed explicitly). If the
command could not be run for any reason, the value is -1
and
an R warning is generated. Otherwise if wait=FALSE
the value
is the error code returned by the command, and if wait=TRUE
it is the zero (the conventional success value),
If intern=FALSE
and wait=TRUE
(the defaults) the text
output from a command that is a console application will appear in
the R console (Rgui
) or the window running R (Rterm
).