.BG
.FN unix
.TL
Execute a Command
.CS
unix(command, input, output=TRUE)
.AG command
any command suitable for execution by the shell.
.AG input
the data to be treated as the input to the command.
If this argument is supplied, its elements are written out, one per line,
to a file, and this file becomes the standard input to `command'.
If `input' is missing, nothing special is done to provide input to
the command.
.AG output
if `TRUE', the standard output of the
shell command will be returned as a character vector,
with each line of output turned into one element of the vector.
If `FALSE', standard output for the command remains unchanged; typically,
to the user's terminal.
.RT
Character vector containing the standard output
of `command' if `output' is `TRUE'.
Otherwise, a numeric value giving the exit status of `command';
exit status of 0 means successful execution of `command'.
.PP
Use `output=FALSE' when the executed `command' interacts with the user.
.EX
# get contents of a file, one element per line
unix("cat myfile")
.KW interface
.KW file
.WR
