| 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.
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 a 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).
B. D. Ripley